THE ~IARSEILLES AND ST. LOUIS ELECTRIC ROAD RAILWAY.

BY C. S. Du R wuE PRELLER, ~LA., Ph.D., A.M.I.C.E., M.I.E E.

THE town of Marseilles now contains, with its suburbs, close upon half a million inhabitants, and in spite of the narrowness, the sharp curves, and the steepness of many of its older streets, pos-sesses one of the largest tramway systems in F rance. The system, whose aggregate length is upwards of f01ty miles of double line, is owned and worked by the Compagnie Geoerale Francaise, which also owns the tramways of Tours, Orleans, Havre, Nancy, and Genoa (Italy); and the con-

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E N G I N E E R I N G. w~nds charged with moisture, is frequently so shppery that a great deal of the useful energy of the horses is l~st; so much so that the average work per horse 1~ only about twelve miles per day, as compared w1th twenty-two in some of the other large towns mentioned. Under these circumstances the company tried, on the new suburban exten~ sions constructed since 1890, various systems of mechanical traction, such as R owan's steam cars Me~arski's compressed air cars, and tramway loco~ mohves. The steam cars did not give very satisfac-tory results and were diticontinued, one of t he principal reasons being that the consumption of coke, which was about 3 kilogrammes per car kilo-metre (10.6 lb. per car mile) as long as the boiler

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cession was granted for fifty years, the municipality having the right of purchase on the principle of valuation by experts. The older lines- viz., those in the town itself, have always been, and are still, worked by horse traction, the cost of which ( 40 centimes per car kilometre, or 6.12d. per car mile) exceeds, however, considerably that in other large towns in the South of Europe, such as Lyons (35 cents. per kilometre, or 5.35d. per mile), Bordeaux (32 cents. per kilometre, or 4. 9d. per mile), Toulouse (30 cents. per kilometre, or 4.6d. per mile), Genoa (29 cents. per kilometre, or 4.43d. per mile), Turin (27 cents. per kilometre, or 4.13d. per mile), Milan (25 cents. per kilo-metre, or 3.82d. per mile), and Florence (25 cents. per kilometre, or 3.82d. per mile).

The comparativ~ly high rate at ~Iarseilles is owing, to some extent, to the unevenness of the ground, but, more especialJy, to the fact of the town being paved exclusively with porpbyrit!c granite, which is not only exceedingly hard, but, under the influence of the prevailing south-easterly

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t ubes were clean, was dvubled when, after a fort-night or three weeks, the tubes became in-crustated, so that the expenditure for fuel alone amounted to 25 centimes (3 8d.) per car mile ; while the compressed air cars, in order to accommodate the traffic, had to be made so large and heavy (14 tons) that in the crowded and narrow streets of Marseilles they were not considered sufficiently manageable.

A third suburban extension in Marseilles is worked with fairly eatisfactory results by tramway locomo-tives hauling three or four carriages ; but for the most recently constructed extension, that of a road railway from the centre of the town to the much fre-quented locality of St. Louis, north-west of Mar-seilles, the company adopted electr~cal traction by motor cars with overhead wires, and let the con-tract for the construction and equipment to Messrs. Sa utter, Bar le, and Co., of Paris, and the Oerlikon \Vorks, of Zurich, the contractors guaranteeing that the cost of traction should not exceed 22 centimes per car kilometre, or 3. 36d. per car mile, which limit

499 was subsequently raised to 28 centimes per car kilometre, or 4. 28d. per car mile. Both the elec-trical installation and the working of the Jine had to be adapted to the peculiar and capricious traffic of Marseilles; and the railway, therefore, presents not only several characteristic, but, as regards working experience, some very instructive fea-tures.

Line.-The railway (4ft. Si in. gauge) is 6 kilo-metres or about 4 miles in length, and, with one exception, is double throughout. I t starts (see map, Fig. 1, and section, Fig. 2) from the well-known central thoroughfare of Marseilles, the Cannebiere, about 6 metres or 20 ft. above sea level, and runs up the narrow Rue d' Aix with

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grades of 5 to 6 per cent. , then falling, traverses the industrial suburb of St. Lazare with inclines of 2 to 4 per cent. , and then passing through the suburbs of Les Grottes and La Cabucelle, rises again to St. Louis, a station on the Lyons and Paris Railway, with maximum grades of 3 to 5 per cent. The rise thus represents altogtther 70 per cent. and the fall 30 per cent. of the entire length, throughout which there is not a single level section. On the other hand, the curvature only constitutes 8 per cent. of the total length, while the radii vary in the open line from 113 to 44 metres (5. 6 to 2. 2 chains), and only at the central depot descend to 15 metres or 0. 75 chain. There are nominally three intermediate stations, but the motor cars stop whenever required to pick up or set down passengers. With the exception of the terminals and fixed stations, the two lines are placed through-out in the centre of the roadway, which is 10 to 12 metres (33 ft. to 40ft. ) in width, while in the Rue d' Aix- viz., the most crowded part of the line, the roadway is only 7 metres or 23ft. in width. In this section, about 350 metres (385 ft.) in length, the line is only single, with pas~ing places at both ends.

Permanent 1Vay.- The granite pavement used in the town and suburbs of Marseilles is of the un-usual depth of 18 centimetres (7 in.), and this necessitates a special type of permanent way (see Figs. 3, 4, and 5), which, under similar con-ditions, has also been applied at Genoa. The steel girder rails are an adaptation of the Phrenix rail, but lighter, with a somewhat deeper groove (3. 6 centimetres), and instead of the flange, have a thickened web at the base. They are 10 centimetres (4 in.) in depth, 9.5 centimetres (3. 75 in.) wide at the head, 3 centimetres (1.18 in.) at the base, and the web is 0 95 centimetre (0.37 in.) in thickness, the weight being 27 kilogrammes per metre, or 54 1 b. per yard lineal. In the usual Phrenix permanent way, the rails, generally 16 centimetres (6. 5 in.) in depth, rest direct on the gravel or concrete bed, and are tied by flat iron bars every 10ft. At Marseilles, on the other hand, the rails are supported on chairs which are bolted to Zores cross sleepers. The rails are 10 metres (32ft. 9. 7 in.) in length, and are laid not with opposite, but with alternate joints. The distance between centr5 of sleepers is 1 metre (3. 28 ft. ), and 0.5 metre (1.64 ft.) at each alternate joint, so that there are five sleepers to every half length of rail. The sleepers, "hit:h are 1. 7 metre (5. 5 ft.) in length, weigh 17 kilogrammes (37.4lb.) each, or 29 kilogrammes (64 lb. ) with chairs, and the angle fish joints, 44 centimetres (16.3 in.) in length, have nu less than six bolts and are of peculiar form, clamp-ing the rails at the base, as shown in the illustra-tion. The permanent \vay is thus entirely of steel, and weighs complete 85 kilogrammes per metre, or 170 lb. per yard lineal, as against only 82 kilo-grammes or 164 lb. of the ordinary Phrenix girder permanent way.

The steep grade section in the Rue d' Aix, where a ~lipper brake is used, is laid with 27

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kilogrammes 54 lb. flange steel and guard rails, resting on longitudinal ..JI- metallic bear-ings which are bolted to Zore's cross sleepers. This permanent way costs as much as 70 fr. per metre, or 51s. per yard. The girder-rail permanent way, as described, is known in France as that of M. Humbert, the general manager of the company. It is certainly very substantial, but more compli-cated, and also more costly, than the ordinary Phrenix 8ystem, its cost being, including laying, but without paving, 20 fr., as against 16 fr. of the former per metre, or 14.5s. as against 11s. per yard respccti vely. It possesses, however, for electric traction in urban and suburban districts, the great advantage of constituting a complete metallic system which materially conduces to insure the con-tinuity of the circuit through the rails.

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Cent1al Station.-This is situated at 2.2 kilo-metres from the Marseilles and 3. 8 kilometres from the St. Louis terminus, and forms part of the com-pany's great "Lazaret" depot. 'l'his depot (see Figs. 6 and 7, page 500), erected in 1891, and covering no less than 8000 square metres, or 9560 square yards, comprises a three-storey frontal building for offices, dwellings of the staff, and stores ; a machine house, engine, and car sheds, repair shops, two water tanks of a capacity of 200 tons ; a coal shed for 1000 tons, and two outer buildings at present used as stables for 200 horses. The depot serves at present for some of the horse lines, for the line worked by steam locomotives, and for the electric railway ; but it will ultimately be exclusively used as an electrical central station and depot of 1500 horse-power.

Original l ustallation. - ln accordance with the original traffic estimate of the St. Louis line, the steam and electrical plant, as at first put down, comprised (a) three multitubular boilers of Nayer's type of 90 square metres (968 square feet) heating surface, each provided with heaters of 70 square metres or 753 square feet, the maximum pressure in boilers being 12 atmospheres, the working pres-sure 10 to 11 atmospheres, or 147 lb. to 160 lb. per square inch, and the boilers being fed by a steam pump and three injectors ; (b) three vertical and com-pound non-?o.ndensing H offmann_ engines m~de at Oerlikon, g1vmg, at 275 revolutwns per mmute, and 11 atmospheres pressure in boiler, 100 effective horse-power each; a~d (c) three direc~ coupled continuous current b1polar dynamos w1th drum armature of the Oerlikon type, whose output at 550 volts was 66 kilowatt or 90 horse-power each.

N ew I nstallation.-For reasons which will appear hereafter the oriainal plant of 300 horse-power

, b f . th ' proved quite inadequate, and a. ter s1x mon s working experience had to be e~t.trely re!llodelled. In the new installation, the ortgmal botlers have been retained, as they easily vaporise up to 2000 litres, and on an average 1600 litres, or 3500 lb., ..of water per hour each, or 4. 8 tons per hour total,

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BARR'S CONTRACTING CHILL AND GRINDING MACHINE FOR CAR WHEELS.

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horae-power. A fourth boiler for reserve is, how-ever, to be put up shortly .

The three vertical high-speed Hoffmann engines have been replaced by three horizontal single-acting condensing Corliss engines (two large and one small) made at Van der Kerchove's works at Ghent. The diameter of cylinders of the larger engines is 56.9 centimetres (22 in.), that of the

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cent., and 160 hor se-power at 17 per cent. ad-mission. With the H offmann engines, the m ean consumption of fuel varied from 2.5 to 4 ki~o . grammes, or 5.5 lb. to 9 lb., and that of steam as much as 20 kilogrammes (44 lb .) per hour per horse-power, so that here, as in some cases else-where, the work done by these high-speed engines was by no means economical. The Corliss engines are guaranteed at twelve atmospheres pressure in b oilers to work with a consumption of steam not exceeding 9 kilogrammes (20 lb.) per horse-power per hour from full to no load. As will be seen later on, the variations of load on such a line as

t~at of M l\rseilles are enormous, and in view of this the Corliss engines are further guaraateed not to vary in speed more than two revolutions from full to quarter load within two minutes.

The condensed water, on leaving the condensers, is collected in a small tank from which two suc-tion pumps, actuated by toothed gearing from the shaft of the small steam engines, drive it into a Sec refrigerator (see Fig. 7). This latter consists of a series of pipes arranged in a hori-zontal plane on the top of a reservoir, and pro-vided with spray jets through which the water is forced up to a height of 3 to 4 metres (10 ft. to

. 13 ft. ), its temperature being, by simple contact with the air, r educed from 45 deg. to 25 deg. Cent. (112 deg. to 76 deg. Fahr. ) . This refrigerator is constructed for a m~ximum refrigerating capacity of 150 cubic metres or tons of water per hour, and surmounts the sheet-iron r eservoir of 300 cubic metres or tons caplcity, supported by iron columns and placed on the top of the coal shed.

The three 100 horse-power bi-polar direct-driven dynamos have been replaced by belt-driven four-polar Oerlikon dynamos (Fig. 8) whose drum armatures are series and compound wound with cross-connections in the commutator, the double winding being inserted in mi~a pld.t~ insulations fitted in grooves or slots of the armature core, while the commutators are, not of bron ze, but of hard laminated copper. The two large dynamos give at 300 revolutions per minute and 550 volts, a mean output of 206 kilowatt or 280 horse-power, whilst the smaller machine at 350 revolutions and t he same voltage gives a. mean of 103 kilowatt or 140 horse-power, total 700 horse-power, equal to 93.5 per cent. of the engine power. The disadvantage of belt driving is thus fully com-pensated by the greater efficiency obtained as against the original dynamos driven on the same shaft by engines not adapted to the extremely variable loads. The dynamos also drive a small 5 horsepower motcr of the repair shop. In the cables between the dynamos and the s witchboard a fusible wire is introduced to protect the dynamos in case of short circuit.

(T o be continued.}

THE DEVELOPMENT OF SOUTH AFRICAN RAILWAYS.

(Continued from page 328. ) THE configuration of South Africa, though at

first sight suitable for rail way purposes, consisting, as it does, mainly of vast plains, separated by ridaes of hills, rarely risi ng to mountains, running pare:ulel for the most part with the coa~t lin.e, is really far from suitable. For these plams he. at various elevations in a series of steps, and the rise from one to the other is generally very sudden and abrupt. And the plains . themselves are. by no means level plains, and the1: surfaces offer In ~any cases inclinations as rapid as the maxtmum gradient. The peculiar dryness o.f the climate of the Cape is in rail way as well as agriCultural matters,

' h . d t , '' the cause at once of all t e1r woes an wan s. The country has b een g radually denuded by bush fires and careless tree-cutting, and this has intensi-fied the action vf the sun and the desert winds, till the greater part of the land of the colony is glazed with baked clay, from '!'hich t.he water .runs ?ff as fa

OcT. 27, 1893.] dina.l seats on each side, with a total seating accommodation for thirty-eight passengers. The platforms at each e_nd are 2 ft. 3~ in. long, with entrances at each s1de protected by wrought-iron gates of neat design, and strong wrought-iron hand-railing. At the centre of each platform provision has been made for crossing from one car to another by means of a hinged cheq uered plate.

The underframe is constructed of channel steel of the same sections and general desian as the first-class carriage before described. The bogies are also of the same design as those of the first-class carriige, with the addition of a brake acting on all the four wheels on each bogie. The whole of the body framing, outeide panels, and mouldings, are of teak. The roof is made double, and with sun screens extending the full length of the body. The seats and backs are made in lath and space of pitch pine and teak, got up with the natural grain and varnished. The head panels over the win-dows ioside are of teak, with teak mouldings. There are ele""Ven windows on each side, glazed with 26-oz. sheet glass fixed in sliding frames of teak ; also blinds of venetia.n type made to slide the same as the glass frames. Over five windows on each side, hit-and-miss ventilators are provided ; a small water tank for drinking purposes is fixed at one end of the carriage at a suitable height above the platform. Central hinged doors divide the interior from the platforms. A powerful screw brake is fixed at one end of the carriage, acting on all eight wheels.

The whole of this r olling stock has been con-structed by the Brush Electric Engineering Com-pany, Limited, at the Falcon Engine and Car " ' orks, Lough borough.

(To be continued.)

THE BRITISH ASSOCIATION. (Continued jr&m page 478.)

THE TE.iCBING OF SCIENCE. SEVERAL paper.3 of an educational charac~er we;:e

brought before the section. The most important one was that by Professor Carey Foster, F .R.S., Dean of University College, "Apparatus for Ele-

m~ntary Class \Vork in Practical Physics. " Pro-fes~or Foster took the trouble to exhibit some of his apparatus for the practice of his students, and to demonstrate their use. The students, he empha-sised, should take part in the experiments at an early stage. Hence we needed simple inexpen-sive apparatus readily multiplied. The designer of such certainly deserves the greatest praise. Pro-fessor Carey Foster's demonstrations were highly appreciated by the learned professors and less learned m em hers.

E N G I N E E R I N G. such instruction has risen from 173 to 788. Of the scholars under the School Board of London the number of those joining the science classes has ~isen from 2000 in 1891, to 2G 000 in 1892 and 40 000 in 1893. The miefortune of' all such deb'ates Pr~fessor 0. Lodge put in, is that the head masters' cannot be compelled to listen.

A pa_Per by ~ord Ray leigl1, ''A Simple Interference E~per1ment, may also be mentioned here. In th1s apparatus, light from a single slit illuminated by the sun or a lamp, passes down a tube a foot long, and falls on two very fine slits, very dose to one another. An eye placed at the back of the slite sees beautiful bands. The eye replaces a lens. In our eye we ha~e, afl Mr. Glazebrook remarked

after~ards, a lens and a screen, so that, in mA.ny exl?e~1ments, a telescope can be dispensed with. ThlS 1s a fact not generally recognised.

THE P u BLICATION OF S c iENTIFic PAPERs. This is another question constantly forcina itself

upon the_ atte~tion of every man interested i~ pure and apphed sctence. The discussion which a. paper of the above title, by Mr. A. B. Bassett, F.R.S" called forth in Section A, elicited, at any rate, the news that the R oyal Society is aware of the urgency of the question, and ready to do something. Mr. Bassett was not present. He deals with two main schemes : firstly, all papers of importance sho~ld b_e p_ubli~h~d in a central organ- hardly

~eas1ble, 1n h1s op1n10n ; secondly, a digest contain-mg an abstract of such papers should, from time to tinu', be published. For this purpose authors sho~ld append a headnote to their papers, briefly settmg forth the object of the investigation. Such headnotes should be copied and arranged every three or four years, and a digest published. Mathe-matic_ians could ~uy their mathematical digest, chemists the chem1cal one. This is what the Incor-porated Society for Law Reporting has been doing for years. Mr. Bassett thinks that an arrangement could be made, perhaps, with NatvTe, and suggests a committee of the British Association. Mr. J ames Swinburne wished to bear in mind what amateurs did for science, and alluded to the ueages of societies. The actual reading of papers was un-necess9.ry, the expense cf publication was often underrated ; he hoped the Physical Society would take the matter up. Professor Fitzgerald repudiated the idea of an index, abstracts were needed ; a translation of Wiedemann's Beibliitte1, which published excellent abstracts, might go a long way towards solving the difficulty. Professor Rucker concurred. Professor Carey F oster re-minded the section that the reports of the British Association committees did a great deal of useful work of this kind- the decriers of the British Association often forget this. L ord Rayleigh agreed that abstracts were needed. A translation of the Beibliitte1 would, however, not satisfy him. The chief difficulty in all such procedures was the exercise of censorship ; the Royal Society, which he repre-sented as secretary, had already appointed a com-mit tee. Mr. Glazebrook, in closing the discussion, remarked that the problem was one for the whole Association. It is indeed, and for the technical press as well . Something like a thorough reform is needed if scientists and practical men are not to waste half of their time in searching for what may be hidden concerning a particular subject in all sorts of papers under all sorts of titles.

GRINDING .AND PoLISHING OF GLAss S uRFACES.

Mr. \V. B. Croft's paper, "Physics Teaching in Schools," dealt more with the general features of a scientific and practical training. At his school in \Vinchester the suggestions of the Duke of Devon-shire's Committee of twenty years ago are acted upon, according to which simple mechanics, heat, and hydrostatics fall to the second year, chemistry to the third and fourth, geology to the fifth, elec-tricity to the sixth, acoustics and optics to the seventh year. The curriculum requires seven years' attendance, the two last years being essentially de-voted to practical demonstration. In another paper, read on a different day, Mr. Croft described "Simple Apparatus for Observing and Photograph-ing Interference and Diffraction Phenomena." The photographs which he threw on the screen proved that his simple apparatus answered remark-ably well.

Mr. A. E . Hawkins, of Bedford, referred, in his " Notes on Science Teaching in Public Schools," to the examination craze, which is now being abused at almost every meeting of teachers, and yet appears so firm ly established. There is a whole literature living simply on examinations; we have examiners, fees, grants, prizes, and scholarships ; the system offers too great advantages to some of all classes concerned. This, however, is not what Mr. Hawkins said. He demanded ample time for the science teacher to prepare his experiments ; appa-ratus for the boys, who should take comprehensive notes, &c. The discussion showed that competent men, Mr. Glazebrook, Professors Fitzgerald and 0. Lodge, Mr. De J ones, Mr. Emtage, Dr. Glade ton(.), also differed from the Science and Art Department, and would prefer inspection to examination. Dr. Gladstone gave some very interesting figures about the progress of elementary science teaching. During the past two years, the number of schools imparting

Lord Rayleigh's most interesting account of some of his recent work proves that grinding and polishing Are two entirely different operations. A properly ground glass should not show scratches, but detached pits, produced by the pressure of the emery particles, both the glass and the emery being disintegrated during the op(.)ration. Simple grinding produces extraordinarily good results ; ground lenses, and even plane glasses, have re-markable definition, the s un's edge appearing as sharp as when seen through a cloud, but there is great loss of light from irregular reflection. Grind-ing is comparatively easy and quick work; polishing with tool, pitch, and rouge a very tedious and deli-cate task. But we cannot dispense with the latter. Lord Rayleigh ascertained, by weighing and inter-ference observations, how much of the surface depth can be and must be removed by polishing. \Vhen 2.5 wave lengths of the sodium line have been rubbed off, a good polish is obtained; four wave lengths give a complete polish. The polish-ing wears down the surface to the bottom of the

503 pits. This is an almost molecular removal of sur-face molecules ; but Lord Rayleigh did not hold out any h?pe to Professor Fitzgerald, who wished to determme molecular dimensions by counting the strokee, . &c. Hydrofiuoric acid may perhaps help us to qu1cken the polishing process. The acid eats away tho surface in so regular a manner that 0.5 and ev~n 0.1 wave length may thus be removed. The aCld attacks the surface, and widens the pits finalJy leaving a sort of cell structure. Anothe; mathematical paper by LOJ d Rayleigh "The Theory of Reflection from Corrugated S~rfaces," had reference to these investigat!ons.

Co~ TRUCTION OF SPECULA FOR REFLR

E N G I N E E R I N G.

BALDWIN LOCOMOTIVES AT THE WORLD'S COLUMBIAN EXPOSITION. (For Description, see Page 507.)

F ig. 1. -. .. -- .

Fig. 2 .

F ig. 3.

Mallard, Daubree, and Friedel in the supposed that cane-sugar is the first sugar produced during His own work on " Thiourea " has proved to him meteorite of the Canon de Diablo in Arizona. the assimilation of carbon, and t hat starch is formed how many times derivatives are re-discovered and Other events are Dr. P arkins' researches on at its expense as a reserve material. Important imperfec~ly identifi.~d. The remedy, or one remedy, electro-magnetic rotatio~ ; Lord R~yleigh's .on the are also the researches of Cross, Bevan, and Beadle he finds In exhaustive monographs. Comparative density of gases ; Dewar s on chemical reactiOns at on the interaction of alkali-cellulose and carbon chemistry is a vast field. It comprises the colours extremely low temperature; Clowes' on flame-cap bisulphide. The enumeration of these discoveries of certain compounds, and their constitution a measurements ; H orace Brown and Morris on the brings Professor Reynolds to the burning question, problem on which the controversy between A;m-chcmistry and physwlogy of foliage. These latter the utilisation of the vast stores of facts laid up in strong, Hartley, and others may throw light. investigators have come to the startling conclusion the various Transactions, Berichte, Annales, &c.

1 The colours of cert!l.in metals, gold, copper,

E N G I N E E R I N G.

BALDWIN LOCOMOTIVES AT THE WORLD'S COLUMBIAN EXPOSITION. (Fm Desc1iption, see Page 507.)

Fig. 4

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Fig. 6.

more so of nickel and cobalt, whose atomic weights applied Newton1s third law of motion to chemical differ so slightly that the possibility of experimental molecules, regarded as a system of atoms analogous errors is not excluded (Ni 58.6, Co 58. 7), seem to to double stars. He finds that Newton1S three point to complex structure, and perhaps something laws are applicable, " with this difference, that like isomerism. The Rev. Dr. Haughton has taken whereas the specific coefficient of gravity is the up a sugge!tion which Mendeleieff made in his same for all bodies, independent of the par-Royal Institution lecture, May 31, 1889, and has ticular kind of matter of which they are composed,

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the atoms have specific coefficients of attraction which vary with the nature of the atoms con-cerned. 11 Professor Reynolds then passes to the comparative study of carbon and silicon. Carbon whether combined with oxygen, nitrogen, or hydro: gen, is the great element of organic nature whilst Bilicon, in union with oxygen and variou~ 'metals

1

so6 no~ only forms one-third of th~ solid earth crust, but is unq uestionably the m~st 1mpo~tant element of inorganic nature. The chtef functwns of carbon are those performed at comparatively low tempera-ture hence carbon is essen tially the element of the present epoch . The activities of silicon a:re m ost m~rked at very high temperatur.es ; hen.ce 1ts chief work in nature was p erformed tn th e dtstant past when the temperature of this earth was fa.r bey~nd that at which the ca.rbo~ com.poun ds of organic life could exist. Th~ . d1scuss1on of ~he analogies between carbon and sthcon, some of yv htch h ave lono- b een understood, and to which Professor Reynold; has made noteworthy additions, con-stitutes t he main pl.rt of the address. H e ha~ obtained an allyl thiourea, a singularly viscid fluid, which req uires several days to regain its level w_hen a tube containing it is inverted. The P!l-per brmgs out an interesting analogy b etween nttrogen and aluminium, molten aluminium freely dissolving silicon. Professor Reynolds regards the many alumino-silicates as final oxidation products of some silico-aluminium analogues to carbon -ni trogen compounds. Those silicates may be regarded. as t eleoxidised representatives of substances whiCh foreshadowed, in terms of silicon, aluminium, and oxyO'en, the compounds of carbon, nitrogen, and hyd~ogen required, at a later stage of t h e earth 's history, for living organisms.

(To be continued.)

BARR'S CONTRACTING CHILL FOR CAR WHEELS.

TnE very great succes. of chilled ca,t-iron car wheels in America lends interest to an account of the chief difficulties found in their manufacture, and the points on which their good service depends. . A per~ect chilled car wheel should meet the foll

OcT. 27, 1893.] :"'

swe1.t, a nd the p resen ce of slag is almost entirely pre-vented. 1 d b f 4 There is a decided im provement m t 1e ept o white iron and in its uniformity arou!ld the tread,. t he averacre variation around the tread bemg about 1'tr m .

E N G I N E E R I N G.

P ARTICULARS Ol.o"' BALDWIN L OCOMOTIVE.' AT THE COLUMDIAN E XPOSITION. ---------- --

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Express Passenger Locomotive, Ameri

c1n " Type, for the Baltimore and Ohio Railroad Company.

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Compound Expre.~s Pa.ssen ger Locomot 1 \e,

" American " Type, for the ()en tral }tail

road Company of New J ersey.

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Compound Frei~bt Locomotive ''Con solidation " Type,

for the Norfolk and Western Railroad

Company. - - -------

5. ,~ , " 5t " 4t , " 4! " 48 in.

78 in. 36 ,

8 in. by 12 in . 5! " " 8 , il! , , 5! ,

48 in.

50 in. 30 "

7 in. by 8 in . 4,, 8, 5~ , , 6 "

31 io. and 34. in.

Descript ion of boiler . . . . . . . . . . . . . . . . Straight Inside diameter of smallest boiler ring . . . . . . . . . . 68t in.

Wagon top 56! in.

Belpaire. 58i iR.

Material of barrel of boiler. . . . . . . . . . . . . . Steel Steel Steel. !I Thickness of plates in barrel of boiler . . . . . . . . . . t'~I m . .

1 Butt jointed, witb Butt jointed with Butt joint, s1x rows Kind of horiz~ntal seatr s .. .. .. .. .. . . double coreriog double ~overing of rh.ets, & ~ouble \ strips strips covenog strtpe. , circumferential seams . . . . . . . . . . . . Double rivet

so8 ELEVATORS AT THE 'VORLD'S

COLUMBIAN EXPOSITION. 'YE illustrate on the present page a very neat worm-

geared belt elevator shown at the World 's Columbian Exposition by the Eaton and Pr~nce Company, of. 7~, 1Iicbigan-street, Chicago. It w1ll be seen that 1t 1s driven by open and crossed belts in the usual way, and that the worm is inclosed in an oil box. Both the worm and wheel are carefully cut. The end thrust of the wormshaft is taken by a steel pin let into the end of the shaft, and running against hardened steel buttons in a special oil chamber. The drum is grooved to take the rope in an orderly manner, and the oppo-site end of the drumshaft carries a governor, which, on the normal speed being exceeded, puts the hand-rope wheel in gear with the shaft, and shifts the belt on to the loose pulley. In connection with the strik-ing gear, there i3 a brake which acts on the foot pulley. This is always in action vrhP.n both belts are on the loose pulleys. There is also an arrangement, shown i_n the engraving, by which the mechanism is st opped 1f the hoisting rope becom()s slack.

The same firm show also the steam freight eleva.tor illustrated in Fig. 4. It will be seen that the engine drives the hoistin~ gear by means of a short be~t, which is kept tight by a jockey pulley riding on 1t. The hoisting drum is grooved to take the wire rope, and ha9 one flange extended to serve as a brake pull()y. The brake can be applied by the hand rope, or by the hoisting rope becoming slack, due to the cage sti_cking in the well in descending, or by t he governor, 1f t he normal speed is exceed~d. This governor is mounted on a side shaft, and driven by a pitched chain. The engine has two cylinders, and will start in any posi-tion, the steam being distributed by ordinary D valves.

SALADO BRIDGE, BUENOS AYRES AND ROSARIO RAILWAY.

\VE illustrate on our t wo-page plate the bridge over the River 1 alado, recently erected near the city of Santa F~ on the Buenos Ayres and Rosario Rail-way, a line for which Messrs. James Lh~esey anll Son are the consulliing engineers. The total length of the bridge between faces of abutments is 6733 ft. 9 in., or 1. 27 533 miles, and is divided into 80 approach spans of 65 ft. 3 in. (Figs. 9 to 14), and 12 main spa.ng (Figs. l to 8) of 126 ft. 6 in. The approach spans are carried upon cast-iron screw pile piers (Fig. 15), and the m:tin spans upon wrought-iron cylinder piers, filled with concrete (Fig. 16), the t otal height of the former varying from 28 ft. to 34 ft., and the latter from 59 ft. 4 in. to 49ft. 4 in. The main girders in both spans are of the inverted " 'arren type, with trough top and bottom booms, and angle and t ee iron diagonals ; the cross girders a re of plate and angle iron, and t he rail bearers of channel iron , formed as shown, a section that in t he event of derailment is of the greatest possible service, as has already been proved on the bridge, by the wheel taking the inside of the trough. Expansion is provided for at one end of each spa.n. The gauge of the railway is 5 ft. 6 in.; the rails are of Yignoles section, secured by coach screws and clip washers to the wooden sleeper blocks, they in their turn being bolted to the bottom of the rail-bearers. The wrought-iron cylinder piers are 8 ft. 6 in. in diameter below and 6 ft. 6 in. in dia-meter above the cones, the depth of the lower rings being :3 ft. 4 in., and the upper 4 ft., the thickness of the plating varying from ~ in. t o i in. ; the joints, both horizontal and vertical, are covered with bar and t ee iron, and the top and bottom rings are stiffened by an internal angle iron. As previously stated, the cylinders are filled with concrete on which the cast-iron bedplates carrying the superstructure rest; between each pai r of cylinders are two stiffening girders and brackets, and each cylinder is surmounted by an orna-mental cast-iron cap of !-in. metal resting on a cast-iron moulding bolted to 'the cylinder. The piers carrying the approach spans are formed of cast-iron piles 2ft. 6 in. in diameter in the shaft, and 4 ft. 1 in. in uiameter of screw blade, they are of 11-in. metal, and average 10 ft. in length ; each pair of piles is firmly braced with a bracing formed of plate and angle iron, secured by bands clipping the piles; on the top is a pile cap, and on this rest the main girders, which are bolted t o the cap. The total weight of ironwork in the bridge is 4800 tons. The main spans and piers were manufactured by Messrs. " "est wood, Baillie, and Co., of London Yard, Poplar, London, E., and the approach spans and piers by 1\1essrs. Cochrane and o. , of \Vood-side Iron Works, Dudley.

The line of railway is somewhat prolific in long bridges, as, in addition to the one now under notice, there is a five-span bridge at 606.235 kilometres, on masonry piers, an eighteen-span one at 484.920 kilometres, on screw pile piers, and a thirty-five span one over the Sali Ri vcr, on masonry pi era ; these are all 65 ft. 3 in. span, and the total weight of ironwork in these three bridges is 1250 tons ; they were all manufactured by the Patent haft Company, of W ednesbury. There is also the bridge over the Dulce River, ninety spans

E N G I N E E R I N G. [OcT. 27, 1893.

ELEVATORS AT THE WORLD'S COLUMBIAN EXPOSITION. CONSTRUCTED BY THE EATON AND PRINCE COi\IPANY, ENGINEERS, CHICAGO.

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of 66 ft. 3 in., on cast-iron screw pile piers, of a total weight of 2500 tons, manufactured by Messrs. Cochrane and Co. , of Dudley. The last four referred to were all" deck " bridges, and, including the subject of our notice, were constructed from the designs and specifi-cation$ a.nd manufactured undet the personal super-

vision of :Mr. Jonathan Packma.n, ~1. Inst. C.E., 63, New Broad-street, London.

GERMAN CANALS.-A CA.nal is proposed between Dort-mund and Ems. The canal will pass vid Ruhrort, Duis. b'urg, Mulheim, Essen, Bochum, and Herne,

ENGINEERING, OCTOBER 27, 1893. -

THE SALADO BRIDGE; MR.

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(.For De.sc1'iption, see Page 508.)

AND ROSARIO LONDON.

RAILWAY.

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E N G I N E E R I N G. 509 THE CYRUS ROBERTS RAILWAY HAND-CAR ; COL UMBIAN EXPOSITION.

CONSTRUCTED BY MESSRS. ROBERTS, THROP, AND CO., THREE RIVERS, MICHIGAN, U.S.A.

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H AND CARS find a widely extended use on American ra ilways, owing to the immense distances to be patrolled, and t he wide intervals separating the sta-tions. Hence very considerable pains are expen ded in making them light a nd easy to drive, so that the men may get to and from their work with a moderate amount of exertion. There are several types on view at the Chicago Exposition, one of which we illustrate on the present page. This is known as the Gyrus Roberts combination walking beam hand-car , and is constructed by Messrs. Roberts, Throp, and Co., of Three Rivers, .Michigan. The driving is effected by a. walking beam, with a hanrlle at each end for two men to work. T he walking beam and ' ' gallows " frame can be removed in less than a. minute, leaving a free surface for push-car purposes. A clutch gear can be thrown out of gear to release the propelling mechanism. This car is especially serviceable for track patrol, emergency cases, wash-outs, &c. ; it is built with a. trussed frame, d iagonal truss rods with turnbuckle attachments for imparting rigidity to the frame and squaring the axles, a nd steel pedestals with dust-excluding brass boxes for t he axle journals. The car is mounted on the Gyrus Roberts ligh t steel hand-car wheel shown in Figs. 2 t o 4.

BALANCING ENGINES. 'ro T ILE EmTon Ob' :BNa iNEERINc.

8IR,-In your number of September 11, 18!)1, s ix months before the reading of Mr. Y arrow's important paper on the balancing of engines, you described an arrangement which I intended to use in order to destroy vibrations on board over powered light vessels.

It may interest your readers to know t hat I have j ust tested the arrangement for the first time on the double-screw torpedo-boat the Chevalier, of 115 tons displace-ment, officially tried at Cherbourg last week.

At all speeds~ up to 27.22 knots (mean of one hour, and perhaps the highest ever recorded ) t he vibrations were found to be unusually small . As the valves and pumps are not balanced, some slight motion (a. great .Part of which is due to the screws} still remains, but it Is quite unimportant, and the writing on the notebooks shows no appreciable difference from what it would have been on shore.

Ib may be wor th recalling the principle of the improve-ment. The engines are triple-expansion, with three cranks at 120 deg.

The weights of the three pistons, piston-rods_, a.nd con-necting-rods are identical and it is remarkable tba.t in this case the sum of the three forces of inertia is always nil, 'Whatever be the length of the connecting rod.

Let F be the force of inertia. of the moving parts of one cylinder in kilogrammes.

P the weight of these moving parts (piston, piston-rod, a.nd about on6-half of the connecting-rod ) in kilogrammes.

G the stroke in metres. m the ratio of the length of the connecting-rod to

that of the crank. n the number of revolutions per second.

I

large aeroplane attached t o the machine, so thab, no matter what accident should occur, the machine could not fall with sufficient rapidity to produce a destructive shook. The large aeroplane will certainly prevenb a rapid fall. It can also be made to do a portion of the 1 fting.

My machine is provided with both long and narrow aeropla.ne3 for doing a part of the lifting, and a very large aeroplane, principally designed to prevent a too rapid fall. Mr. :Phillips is of the opinion that a machine might be so manipulated in the air as to prevent a. fall even when the machina is not provided with a large aero-plane. I admit that this id quite possible, and I thiok that Mr. Phillips must also admit that a machine without a. large aeroplane might, if stopped in the air, descend to the earth at a very high velocity. I am the exponent of a combination of narrow superposad planes and a large aeroplane.

A9 long ago as October, 1892, I wrote an article which appeared in the Fortnightly Review, from which I quote the following :

"In constructing a. flying machine which is intended to be navigated by 11 ving engineers, precautions must be taken to in ure their safety. A very large aeroplane has to be provided to prevent a too rapid fall in ca.se of a atoppa.~e of the machinery, and this, of course, adds to the we1ght and to the power required to drive it. But should a flying machine be consid~red as only an aerial torpedo for carrying high explosives and dropping them at a. poinb 20 or 30 miles distant, then the bulky aero-plane C()uld be replaced by a large number of long narrow blades or wings placed one above the other (superposed), which would lift much more for thei r weight, and the power required to drive them, and would enable the machine to fly much faster. A machine of thij:! kind could be governed as relates to height above the earth, after the manner of a common water torpedo, while its direction could ha controlled with a great degree of nicety by a magnetic needle operating upon automatic steering gear constructed in such a manner that it could instantly be l:iet to steer automatically to any desired point of compass, and the machine could be made to let go its bomb, or to fall itself with the remainder of its naphtha., after the screw had made a. predetermined number of turns."

This, I think. ought to set at rest for ever the question as to whether I am an ex ponent of a very large aeroplane or of a. large number of long and narrow planes.

Y ours truly, HlBA~I s. MAXIM.

Bald wyn's Park, October 24, 1893.

DIMENSIONS OF TEST SPECIMENS. To THE EDITOR OF' E NG INEERING.

SR,-Thedimensions of a. test piece comparable with the bye-bar 2g in. by 10 in. by 50ft. long, instanced in your article ot October 20, namely, a. sp~cimen ~ in. by ,~ in. by 8 in., is a striking instance of the absurdity of the atterppt to obtain geometrically similar, and, therefore, comparable specimens.

The direct comparison of tests on specimens of an 8-in. or any other 8tanda.rd length and of various cross sections is totally misleading, as pointed out by yourself. The error arises, however, wholly from th~ facb that the exten-sion or elongation is measured and recorded in a manner well calculated to disguise the truth.

The subject has been lucidly treated by Mr. J . H. Wicksteed, in a. paper read before the British Association at L eeds in 1890, and also by Professor Dwelsha.uvers-Dery, of Liege. I will endeavour briefly to make plain the method by which tests of different and dissiruilar speci-mens can be rationally compared.

The extension of a test-piece under stress is of two kinds-firstt a. general elongation of the specimen over its whole langtn between the shoulders, and which elonga-tion continues up to the point of maximum load, and is strictly proportional to the length of the specimen ; secondly, the local extension due to the "striction " or contraction of area. about the point of fracture, and which takes place under a decreasing load. This loca.l extension is entirely independent of the len~th of the specimen, and is dependent on the cross-sect10n of the specimen, and is probably best expressed in percentage contraction of area.. All that is necessary, therefore, is to record the maximum load, and to record the two extensions separately, namely, the extension up to the point of maximum load, and that due to contraction of area. This gives a.t once the results of a test immediately and truly comparable with ~very other test recorded in the same way. The method of expressing the total extension of a specimen in a percentage of the ori-ginal length is both misleading and irrational, for that portion due to local elongation has no relation whatever to the length.

L eeds,

Yours, &c., CH&ISTOPHER W.

October 23, 1893. J Al\IRS.

THE LOSS OF H.M.S. "VICTORIA. " To TII~ EDITOR OF' ENo rN&ERING.

StR-Your two courageous articles on this national oalam'ity go far to checkmate the Admiralty authorities in tactics of secresy a.nd delay, always adopted by them when more than usually gross inefficiency is to be hidden from view. The ordinary course (when such a. matter is beyond pigeonholine-) is for official mouthpieces to promise fullest inquuy and pe.rfect fran~ness tow~rds the public. The popular press 1s thus sa.ttsfied, but 1f a. more than ordinarily Jjersistent organ return to the sub-ject, or if a member of Parliament ask a. que~tion, dozens of exC'uses are ready to hand; the favourite, "delay a.t the

printer 's"-subterfuges so miserably flimsy, it is wonder-ful those pretending to pose a.s honourable men can father them ; more wonderful to expect belief.

It is rumoured, darkly, the desiga of the Victoria. is to be vindicated, in spite of her going down like a stona, though her captain and crew thou~ht she would keep afloat, by the statement that watert1ght bulkhead doors were open; the assumption left for the public to draw being that this was altogether an unusual circumstance, and that the doors should properly have been shut. Tbis is an effort to shift blame from the shoulders of authorities ashore to the backs of those afloat. The absent are always wrong, and the sailor's b1ck is thought broad enough for any burden, but I would like to ask if it be not a. fact, though the order to close watertight doors may be given with the call to general quarters, nevertheless, the doors are immediately again opened, beca.u.se i t i s prac-t ically impossible to carry on duty w tth the doors closed! If that be so in peace manreu vres, such as steam tactics, far more impossible would it be to keep these doors shut during the multifarious duties, together with confusion and exr.itement, of a sea. fight. In short, are not water-tight doors known by sea. commanders to be a sham, put in for paper reasons, that the statement may be made, "the ship is divided into so many watertight compa.rt menta, any, two, three, or four (or half a dozen, as the

ca~e may be) of which can be filled without the vessel sinking., The Victoria as described, and the same ill -fat(\d vessel Rtrickeo by the ram of the Camperdown, is an awful example of the difference between paper and actual efficiency.-! inclose my card, but beg to subscribe myself,

Sir, yours obediently, TRIREME.

October 21, 1893.

To THE EDITOR m E NGINEERISG. SIR,- I write on the a.nni versa.ry of the battle in which

every man was expected to do-and did- his duty, with-out fear or favour. Our immortal Nelson could at least depend upon the Victorys of his day keeping above water for a. reasonable time in the worst eventuality. Surely it is not too much to ask of modern science a definition of what is safe or not safe, within reasonable limits, in con-nection with prGtecti ve appliances on ships costmg hun-dreds of thousands ?

Your two admirable articles on the above indicate with truth that we must know the real deficiencies ere we can devise a. remedy. If certain warships are not capable of bearing our colours and men without doubt of grave danger, let us know it, and it may be possible to suggest an effective remedy. If it be desired to ascertain how few or many filled compartments of one ship of the doubt-ful twelve (when water may have been admitted thereto by structural derangement) would capsize her, why not place a. representative vessel, with full war weights on boMd, over a shallow sandy bottom, and pump water in so as to fill all or any such compartments, severally or together, so as to test the really safe canting, &c., capa-city of the particular type under all 1casonable conditions and eventualities?

Means might be adopted to prevent complete overturn while on trial, and appliances could be ready to rapidly fill or pump out the several compartments. It would give a large proportion of the int~rior of one ship "a. wetting,, but this is better than a. wetting of another sort for possibly the whole of the type. Who can expect men to be oomfortable in- not to say effectively fight- a ship when they are doubtful of its stability even under com-para.ti vely "holiday " conditions ?

ENGINEERING has a title to insist upon knowing really what is wrong. that it may help in putting it right.

L et us re-hoist the signal ordered eighty-eight years ago to-day. In matters essential to the welfare of England's Navy, "England expects that every man "-Admiralty or otherwise-this day " will do his duty."

Your obedient S"r nl.nt, R OBERT McG LASSON.

Selhurst, 8. E ., October 21, 1893. To TJn: EmTon o~ E NGINEEHING.

SIR,- In reference to your leader on the Victotia disaster, appearing in your last issue, in which you urge the desi rability of the Admiralty making a public state-ment showing the cause of the disaster, I venture to think that such statement is unnecessary, M no beneficial result can accrue from its publication. Apart from the policy of such a. proceeding, it may be urged that that unfortunate occurrence can have no effect on future designs. Nor can anything new be adduced.

When it is considared that the introduction of the ram created a new arm of attack, and that numerous incidents have occurred to t estify to its effectiveness, the recent disaster comes with no surprise, from a naval architecture point of view.

The testimony of naval expert opinion, all over the world, is unanimous as to the importance of this factor, so much so that the American Navy, profiting by the experiences of the E uropean navies, bes towed greatl atten-tion to this import method of attack.

In their corresJ?Or!ding ships the ram has been altered so as to increase 1ts efficiency, and, it is to be hoped, de crease the possibility of disaster to itself.

The very existence of the ram presupposed that vessels could be disabled or sunk by ramming, and the recent disaster further adds to the pile of testimony as to its immense influence.

If, on the other hand, vessels can be constructed so that, under conditions similar to the Camperdown-Vic-toria incident, they are unsinkable, it must be perfectly obvious that the ram is an unnecessary adjuncb to our fighting ships.

Sir E. J. Reed, you say, has declared he knows of

THE AMERICA CUP. To THE EDITOR m ENGIN&EBING.

Sm,- Your correspondent, Mr. W. Da.vid Archer, Rays that my ca.lculatio::ts (~~NGINE&RING , October 14, 1893) ''tend to show merely that the scale of time allowance adopted by theN ew York Y acht Club does not sufficiently penalise an increase in the sailing length. . . . " If, however, he again peruse my letter, he will see that my adaptation of R~nkine's rules for the speed of steamships proved that time allowance should not be a constant quantity between any two yachts, but should vary with the time occupied on the cour~e, or with the mean speed over the course made by the winning yacht.

The time allowance under either our own or the American system is quite independent of the time occupied.

Again, my calculations did not show that the A merican time ecale had any considerable difference as compared with the Y . R. A. scale, in settling the success of Vigilant. As a fact, it was not the case.

Valkyric: L. W.L =85. 5 .. . S.A. = 10,0t2 ... Sailing L =- 93 ... Rating H3.

Vigilant: L . W .L = 86. 19 ... S. A . = 11,272 ... SailingL = 9G ... Rating162.

These ratings are Y.R.A. formula with t he American sail measurement. Now, although the ratings differ more in ratio than the sailing lengths, Mr. Archer should not have stopped in the middle of the problem, and come to the hasty and inaccurate conclusion he did ; for had he taken the trouble to go a step further he would have discovered that the two time cur ves set the matter nEarly square again. Thus the New York time allowance for 9G, leES that for 93 sailing length, is 2.93 seconds a mile=1.47 minutes on a. 30-mile course, and Mr. A rcher ! hould therefore be scrprised to learn that the Y . R. A . time allowance for 1G2 - 143 rating, is only 3.45 seconds a. mile = 1. 72 minutes on a. 30-mile course.

I, for one, ca.nnot agre~ with Mr. Archer's suggestion that the problem as to the "determination for any given sailing length of the best ratio between the two factors, length and sail area.," should complicate the contest for international honours in the speed of racing yachts. On the contrary, it appears only reasonable that all problems should, as far as possible, be elimi-nated from such contests . . . and that the resulb should depend upon the reply to the simple question . . . vVhich country can produce the fastest yacht of a length previously agreed upon, and driven by a. sail area pre-yiously agree~ ~pon ? I quite acknowledge that a " sail-mg length " hm1t would be far better than the existina conditions, which amount to a load-water line limit and a. '' sailing length " time allowance, but for international honours we ought to stipulate for a. previ()US a.grc:ement both as to limit of load-water line and as to limit of sail area.. What would your engineering readers t hink of an international contest in steam yachts, where one com-petitor challenged and gave his length on water line at 150 ft., brought his yacht out, st eamed about on the Solent measured mile, recorded his times, and even pub-lished details of his en_gines and their effective horse P?Wer ? Then went to New ""ork and raced against the ptck of four steam yachts bUllt purposely to beat him, each and every one of them carrying engines and boilers of 10 to 20 per cent. more power than the challenger'! Yet this is precisely what we Britishers are conceited enough to think thab we can do in the racing of sailing yachts, their horse-power being measured by their effective sail areas. One word more. All Englishmen should protest emphatically against a continuation of the present system of challenging, whereby any individual may challenge (through one of his clubs) for an international race. The challenge should be on equal t erms with the defence (except that its champion has to cross the Atlantic which is ~air an~ equal if the cup a~so cross occasionally), and thts aqua.hty can only be obtamed by several yachts being built to suit the ?hallenge_, and the best y

OcT. 2 7, r 893.] owner would consent, another attempt could ba made with her to capture the

512 E N G I N E E R I N G.

ROLLING STOCK FOR THE BEIRA RAILWAY. CONSTRUCTED A'r THE BRUSH ELECTRICAL ENGINEERING CO~IPANY, LI~IITED, FALCON WORKS, LOUGHBOROUGH.

(For Description, see Page 502.)

F ig. 1 .

Fig. 2.

E N G I N E E R I N G. 1 NOTICE. many times, and thus, strangled at ~ts outset, re-

AGENTS FOR " ENGINEERING." I The New Cunarders ., CAMPANIA" and ., LU- main a silent monument to the perils that beset AuSTRIA, Vienna.: Lehmann and Wentzel, Karntnerstra.sse. those that adventure in untrodden fields. OAPE TowN : cordon an.d Gotch. , CANIA ;" and the WORLD'S COLUMBIAN I t must not be supposed, however, that an Act ~f EDINDURO ll : J ohn Menztes and Co., ~2 Hau.o' e~~treet. . EXPOSITION OF 1893 t t h1s FRA.'iCB, Paris : Boyveau and Chevillet, L1brame Etrangere, 22, Parliament enables its possessor o ca~ry ou

Rue de la Banque; M. Em. Terqu em, 31blaBoulevard llaussmann. The Publl.sher begs to announce that a Reprint la plans with a reckless disregard of the 1nterests ?f Also for Advertisements, Agcnce HaYas, s, Place de la Bourse. now ready of the Descriptive Matter and Illustra- others. On the contrary, he must use a_ll ~h? s~1ll (See below.) f ENGIN'Ir.lr.RING f bl d GBIUIA..'iY, Berlin: Messrs. A. Asher and Co., 5, Unter den Lmden. tions contained in the tasue o o and resources that are availa e to av01 InJurmg

Leipzig: F. A. Brockhaus. April 21st, comprising over 130 pages, with ntne his neibo-hbours, and it is on_ly when he _has done so Mulhouse : H . Stuckelberger. two- page and four single. page Plates, printed f en

OLAsoow: Willia.m Love, . that he can claim exemption rom paymg comp -INDIA Ca.lcutta: Thacker, pmk, and eo. throughout on special Plate paper, bound in cloth. sation. It is hard enough that individuals should

' Bombay : Tha.cker and Co., Limited. gUt lettered. Price 6s. Post free, 6s. 6d. The ordl 1 d b t th t th h Id JTALV . u. l l oepli, Milan, and a.n" post office. -t suffer for the genera goo , U a ey 8 ?U , nary edition of the lssue of AprU 21st 1s out ofpr.u& 1 b b bl It a L"'~RPOOL: Mrs. Taylol', Landmg- Stage. suffer needlessly wou d e un eara e. IS Mc\KCII&sTER: J ohn He.rwood, 143, Dea.nsga.te. - f h ~ h tl full advantage has Nzw ouru WAL&S, Sydney: Turner and Ilenderson, 16 and 18, NOTICES OF MEETINGS. questiOn or t e cour"s W e ler .

Hunter-street. Oordon and Ootch, Geor, 18n3._ .. The Support of BuildioJZ e:," by Mr. reviewina these Acts, he found that if, in carrymg a\era .... esse\'en words. Pa.y ment must a.ccompany a ll orders for William Spencer, F.G.S. Observations on any otht:r r apers in outtheir~tatutorypowers, theydidcreateanuieance, single

0

adverU ements, otherwise thei r insertion cannot be the Transac tions will be a.amissible at the discretion of the chair- that nulsance mu~t be borne with. But they were guarante~d. Terms for di pla.,red arh:e rtisements

analogy between electricity and water, the judge said that when a man had called into special existence an electric current for his own purposes, and discharged it into the earth beyond his own control, he was as responsible for damage which that current did, as he would have been if, instead, he had discharged a stream of water. The court, therefore, held that the prvprietors of the tram way were, at common law, responsible for the injury and inconvenience done to the telephone company. But common Jaw is liable to be overridden by statute law, and it was pleaded by the defendants that, as they were acting under a provisional order from the Board of Trade, they were exone-rated from the consequences experienced in the t elephone ~ervice. On the other side, it was argued that a provisional order did not carry the autho-rity of an Act of Parliament. But the judge held that Parliament delegated its full authority to the B oard of Trade, and t hat the order was an equiva-lent of an Act. As to whether the tramway was constructed with the highest available skill, in the light of the kno;v]edge available at the date of the trial, he said : "It is surely impossible, with any regard to that common sense which, after all, is the foundation of this and many other branches of law, to say that a railway company which was not liable last year, last month, or even yesterday, because until then its undertaking was carried on according to the rules acknowledged to be the best, is liable now, not because those rules have been proved to be altogether wrong in practice, or un-scientific in principle, but because some diligent worker in this department has discovered what is held for the moment to be a large improvement, but may to-morrow t urn out to be only a step in the progress of further advance. " Here, again, we have it laid down that not only may a nuisance be craated in carrying out an Act of Parliament, but it may be perpetuated after efficient means have been discovered for its abatement. Of course this doctrine must be tempered by the common sense which Mr. Justice Kekewich says is the foundation of law. It is not to be believed that the courts would pedantically agree to t,he con-tinuance of a serious injury of part of the popula-tion if it could be shown that it could be removed at a cost that would not be unduly burdensome to the undertaking creating it.

It is well for those who secure Acts of Parlia-ment to remember that while they have a cer ta.in measure of security, their immunity is by no means perfect, and it is not wise to rely on it overmuch. Our legislators enjoy a female lat itude in changing their minds, and annull ing their decisions. If only clamour enough be raised, t hey will revoke the .Acts of the last, or even of the present Session, without any sign of compunction. The case of the so-called " blow-holes " on t he Metropolitan District Railway is in point. A Bill for their construction was drawn up, and passed without opposition , and in due course the ventila-t on were erected. But immediately t hey were put into use in the neig~bourhood of Palace Green there was a universal howl in the daily press, al though similar, or worse, ventilators had been in existence in Euston-road for years. The statutory authority was unassailable in the law courts, but in the next session of Parliament the Metropolitan Board of Works_applied for powers to enable cer tain of the ventilators to be pulled down, and the only consideration shown to the railway company con-sisted in the Board of Works bearing the expense.

It is only occasionally that sufficient agitation is raised to cause an Act of Parliament to be formally cancelled. But it often occurs that some innocent-looking Bill, which passes without opposition, is eventually found to have severely curtailed the privileges conferred by previous Acts. For in-stance, a new smoke abatement law is as binding on those who work under statutory authority as those who do not. Just as private individuals should protect themselves by opposing, before P arlia-mentary Committees, any schemes that are likely to affect them prejudicially, so also is it incumbent on those who hold legal authority to do certain things in contravention of common law, to see that their privileges are not whittled away by subse-quent enactments .

It is questionable whether it is to the interest of engineers t o aid in advantage being taken to t he full of statutory powers in cases where they bear very hardly upon persons who derive no benefit from them. The case of the Stockwell Orphanage, referred to above, is in point. Here was an insti-

E N G I N E E R I N G. tution raised and maintained by voluntary contri-butions, and doing a most admirable work in con-verting into good citizens, children who, from the loss of their parents, might otherwise have grown up very poorly equipped for the battle of life. The presence of a rail way t o Stock well is no possible advantage to this institution, and yet it has to suffer a very heavy loss by its construction, and the iujury is r endered the more acute by the fact that it is not a general one, to be shared by the district. The case is admittedly a hard one, and has excited a widespread sympathy, the effect of which is felt when it is proposed to erect similar power stations in other neighbourhoods. Of course this does not matter to the City and South London Rail way Com-pany ; thoy have got all they want. But to engi-neers, both consulting and manufacturing, who wish to see the electric r ail ways extend, it is important that no unnecessary opposition should be created. H ence it is their interest to exert an influence in favour of peaceful compromise, rather than for an insistance of the full legal pound of flesh, in cases where a strong moral claim to compensation c1n be made out.

PORTLAND CEJ\IIENT. SIXTY-EIGHT years have elapsed since the dis-

covery of Portland cement, and during that interval its use and importance as a structural material has increased w_ith such unprecedented rapidity that at the present time it is almost universally adopted wherever an hydraulic cement is required. I t does no t appear, however, that our knowledge of t he physical and chemical properties of this material ha'i quite kept pace with its increased use.

The divergence of opinion among engineers on many points connected with the testing, manufac-ture, and occasional failure of cement, indicates that its nature and properties are not yet thoroughly understood. Some engineers, for example, are of opinion that the pre~ence of more than 2 per cent. of magnesia in cement produces fatal consequences, while others hold that magnesia may be considered as an inert and harmless adulterant. Some are strongly in favour of exposing fresh cement to the action of the air, or, as it is called, ' 1 air slaking/' before use; others believe that it becomes deterior-ated by such exposure, and so on through many other details.

Each enginePr frames his specification in ac-cordance with his own particular views, and manufacturers have rather a bad time while endeavouring to meet the varying conditions im-posed upon them. Differences of opinion must naturally cont inue to exist so long as our know-ledge of the material r emains imperfect, but there seems good reason to believe that at least sox:ne of t he differences which at present pre-vatl could be cleared up and eliminated. With this end in view we shall endeavour to epitomise and consider, as briefly as possible, the facts bear-ing o!l the subject which have been elicited by expenmenta.l r esearches, or have been established by practical experience.

I t cannot be considered desirable that the engineer should trench upon or interfere with the functions of either the chemist or the manufacturer, and it is to be regretted that a tendency in this ?-irection appears to have recently developed i tself 1n the matter of Portland cement, the chemistry of which is acknowledged to be of the most intricate and complicated character, and the manufacture of which requires an amount of skill and experience peculiar to itself, which engineers cannot be expected to possess. Under any circumstances it is best to leave chemical questions to chemists ; and interference with manufacturers is to be equally deprecated, not only because they must know their own business best, but because the engineer, by unduly dictat ing how the cement is to be manufactured, takes upon himself the respon-sibility which should be borne by t he maker.

M. Le Chatelier has expressed an opinion that there is at present only one way of determinino-whether the judgment passed on a cement by any system of testing, is sound, and that consists in waiting half a century to see how the work stands. This statement cannot be said to be at present with-out some force ; it is, h owever, much too sweeping.

The permanence of the work depends quite as much on the intelligent and judicious use of the cement as on the cement itself ; the want of per-manence, therefore, would not always prove the use of defective cement. F or the reasons already

[OcT. 27, 1893. indicated, we shall not enter upon the question either of the chemistry or manufacture of cement furth er than a brit- f elementary outline.

So far as regards its active constituents, the average composition of good P ortland cement, deduced from a number of analyses (omitting fractions), is as foll ows :

Per Cent. by Weight.

60 22 11

Lime (Ca. 0) .. . Silica (Si 0 2) .. . Alumina (AJ2 Oa)

. .. ... . .. .. .

.. . .. . . .. ...

... .. . ... ...

the remaining 7 per cent. genera11y consisting of small quantities (rarely exceeding 1 or 2 per cent. ) of oxide of iron, sulphuric acid, magnesia, carbon jc acid, potash, &c. The active components, lime, silica, and alumina, are obtained, the first-mentioned from chalk or limestone, and the two latter from clay (such, for example, as is found in the Medway ), and occasionally from clay slate. The chalk and clay, both being in a s tate of minute division intimately mixed tog~ther, and brought to a plastic condition with water, are burned in a suitable kiln, producing a hard, heavy, vitreous clinker, which, when ground to an impalpable powder , is P ortland cement in its anhydrous condition. The production of good cement appears to depend mainly on the degree of heat applied in the kiln , and the time for which it is maintained, both of which can only be deter-mined at present by the skill and experience of the manufacturer.

The chemistry of cement, as before observed, is of an extremely complex character, and cannot be said to be fully understood. For many years Portland cement was considered to be a double-silicate of lime and alumina ; but recent investiga-tors have come to the conclusion that tri calcic silicate and tri-calcic aluminate are its principal constituents, the lime combining with the silica and alumina under the influence of heat in the pror.ess of burning. \Vhen the anhydrous cement is mixed with water, further chemical reactions occur, result-ing chiefly in the formation of hydrated silicate and aluminate of lime, both of which resist the action of water, and in this way the setting or hardening of cement is accounted for.

The usual tests at presen t applied by engineers to cement refer principally to (1) the tensile strength of cement gauged both neat and n1ixed with sand; (2) the degree of pulverisation to which the cement is reduced ; (3) the weight per bushel of the dry ungauged material ; (4) colour.

To these is occasionally added the effect of sub-mergence in water on thin slabs of cement gauged neat, ,i.e., without sand. There are, however, many other points connected with the subject which require t o be investigated before a proper knowledge of the material can be obtained ; the principal of these are as follows : Adhesive strength, chemical analysis, specific gravity, quan-tity of water used in gauging, time occupied in setting or hardening, the influence of sea-water as compared with t hat of fresh water, the effect of heat in accelerating the chemical changes produced by admixture with water, air slaking, testing-machines, and the causes of occasional failures.

As regards the t ensile or cohesive strength, the systematic testing of cement was first introduced about 34 years ago (1859) by Mr. J ohn Grant, M. Inst. C.E., who specified that briquettes of cement gauged neat should at the end of seven days bear a ter.sile strain of 400 lb. on an area of 1! in. x I t in. ( = 2.25 square inches), or 178 lb. per inch. This was shortly after raised to 500 1 b. on the same area, or 222 lb. per square inch. Since then the demand for tensile strength has increased up to 400 lb. and occasionally 450 lb. per square inch ; while 28-day samples were required to bear 550 l b. to 600 lb. per squ:ne inch.

Within the last two or three years, however, the standard for- seven-day samples in this country has been lowered from 400 lb. to 350 lb. per inch, for reasons which will be subsequently referred to.

The necessity of testing the strength of a mixture of the cement and sand was recognised and adopted in Germany for many years before it had received in England t he attention it deserved, and even at present many English specifications continue to omit this test, which is a far more important one than that of neat cement.

I t is difficult to understand why the tensile strength of neat cement should have occupied such a prominent position as a practical test. The n1aterial is very rarely used neat, but, on the con-trary, is generally mixed with large proportions of

OcT. 2 7, r 893.] other ml!.terials, such as sand, shingle, &c., and, even in this condition, is seldom or never called upon to resist tensile stress. . Cement .may be co~sidered practic.\lly as a kmd of mmeral agglutl-nat:>r, and, as such, it is. m.ost pr.oba.b~e that its tensile strength does not 1nd1eat~ ~1ther 1ts cement-ing power. or it~ p~r~anent durab.Jhty- for exa.mp~e, finfl grindmg d1mm1shes t he tensile strength, but In-creases the cementing power ; it is also well known that to produce high tensile strength invol ves over-limina the cement, which is fatal to its durability , and f~r this reason the standard has been reduced to the extent already referred to.

The sand test, as most of our readers know, is made by mixing together one part by weight of neat cement to t hree parts by weigh t of clean sharp sand which has passed through a sieve of 20 meshes and been retained on one of 30 meshes t o the lineal inch . The German standard for the tensile strength of t his mixture 28 days after gaugrng was first (1877) fix.ed at 114 lb. per squa~e inch but this was soon ra1sed to 142 lb., and ultl-mateiy to 222 l b. per square inch. The sand test, a9 may be shown, furnishes additional evidence that the tensile strength of neat cemen t should not be depended upon as a. proof of good quality.

THE TELAUTOGRAPH. THE telautoaraph is the latest invent ion of that

eminent and skilled electrician, Dr. E lisha Gray, of Chicago. As its name implies, it is an instrumel?-t for the t ransmission to a distance of autograph1e writina. I t appeals to the eye as the t elephone does t~ the ear. The latter carves the air into waves of sound, the former t races on paper a fac-simile of the messagd sent.. The performance of the one is evc1nescent, whilst the record of the other is permanent. As the telephone has, for many purposes, superseded the cumbrous telegraph, so in turn may it be assisted and supplemented by the equally swift and more accurate telautograph. In the telegraphic service, dots and dashes some-times get wofully mixed, to the great d isfigurement of words and names ; even in telephonic transmis-sion certain sounds are very liable to be misinter-preted ; but the indications of th~ new message-sending instrument must necessarily be an exact reproduction of the original. It mattt)rs not whether the sender write slowly or rapidly, elegantly or illegibly, in Greek or in Sanskrit, or whether he send figures or letters, diagrams or drawings ; all are reproduced with equal fidelity by the receiving instrument.

It was at the Centennial Exhibition (Philadel-phia, 1876) that the Bell telephon e was first pub-licly shown, and it was on that historic occa-sion that Sir William Thomson (now L ord Kelvin) called it, in a m oment of pardonable en-thusiasm, "the wonder of wonders." While fully agreeing with that ejaculation of the Nestor of mathematical and physical science, we are con-vinced that the telautograph, as n ow developed and shown in the Columbian Exposition at Chicago, is also among the epoch-making achievements of this electrical age.

The problem of transmitting handwrit ing oc-curred to specialists in the early years of electric telegraphy, when it received the attention of Bain, Ca.selli, and others. Cowper in recent years again attacked the problem, and obtained consider-able euccess. His apparatus, however, did not realise the hopes primarily entertained, so that, after creating a passing sensation, it dropped into the limbus of ingenious but unremunerative in-ventions.

Dr. Gray's instrument, on the other hand, seems to offer a thoroughly practical solution to the elec-trical transmission of hand-written despatches, and to be well fitted to meet the demands created by the high-pressure activity of modern life. We had the advantage of operating wit h the telautograph and submitting its capabilities to a few tests. We found that whether we wrote long or short hand, drew diagrams illustrating points in the construc-tion of a tripha~e motor or covered our sheet with the integration of a differential, the receiving pen synchronously responded and gave a faithful copy of the very complex original. In these experiments the t wo parts of the apparatus were connected by a wire whose resistance represented five miles of telegraph wire. A similar apparatus is working every day between Highland Park and Waukegan -a distance of 14 miles.

In the t ransmitting instrument an ordinary lead

E N G I N E E R I N G. pencil is used to write the message. It is attached near its point to two fine silk cords, which ehorten or lengthen according to the motion of the pencil actuating at the same time the mechanism of the transmitter. This m echanism, in turn, regulates the current impulses that are sent along the line to t he distant station, and which t here compel the receiving pen to move in perfect synchronism with the sending pencil. This pen is a short tube drawn t o capillary dimensions at its lower ex-tremity ; i t is held at right angles to the plane of the paper by two aluminium arms, one of which incloses a small rubber tube connected with a re-servoir of ink for the purpose of affording a con-stant supply t o the pen. This pen may be moved up or down , to the right or the left, or completely lifted away from the paper, by merely perform-ing similar mot ions with the t ransmitting lead pencil.

We are n ot told the details of the mechanism by which these remarkable results are obtained; for, although t he devi~es are well covered by patents, wa are assured that reticence is still deemed neces-sary. It is, however, confidently affirmed that both the mechanical and electrical arrangements are as simple a

-sufficient to run machinery indicating from 1200 to 1600. indicated horse-power. Of course, special plant IS necessary to work the process, so that in ma~ing comparison with the ordinary coking establishment, allowance must be made for this extra first cost and upkeep.

The approximate gross value of the process is easily attained. Taking the case of Silesia, we find that in producing 48,000 tons of coke in six:ty ovens 3000 tons of tar are r ecovered each year, which at 2s. per cwt. yields 6000l., and 840 tons of sulphate of ammonia at 11s. per cwt., equalling 9240l.-together 15,240l. To this amount must be added the fuel saved. In Silesia the total production of gas is 36,800 cubic feet per oven per day, and after consuming 20,800 cubic feet in roasting the coal in the production of the coke, a surplus of 16,000 cubic feet remains for other purposes, equal, as we have already indicated, to 57,000 lb. of coal for the sixty ovens, sufficient for 1600 I. H. P. during 18 houra per day at 2lb. per I.H.P. per hour. The value of this coal-about 9000 tons per annum-should be added to the 15,240l. received for tar and sulphate of ammonia, to ascertain the gross value of the residual products. Thi-; does not in-clude the value of the heat utilised in the oven, which is equivalent to an additional 12,000 tons per annum. Silesia is the most favourable return so far as extent of residue is concerned, but the case of \Vestphalia also shows satisfactory re-sults. Sixty ovens there cost in construction 3!,580l., or 576l. each, and the tar and sulphate of ammonia produced in one year's working provided a revenue of 8375l., or about 25 per cent. on the capital invested in the plant.

'rhe other instances given might also be worked out, but it is probably sufficient to show that Ger-many can afford to credit their actual cost of pro-duction with a large sum, the result of the recovery and sale of by-produ:}ts. Of course, this affects the selling price of their iron and steel, and offers at least a partial explanation for the low quotations made l>y German makers in competition with British manufacturers. The influence on the price of tar and ammonia of the 3000 ovens in use in Germany and Austria is pronounced. In 1883 sulphate of ammonia was worth 16s. per hundred-weight, but now sells at 11s., and tar has dropped in price from 3s. t o 2~. per hundredweight. The decline in prices need not, however, be very alarm-ing, and if, as in the case of Westphalia, four years' revenue suffices to pay for the plant, it should not be excuse for rejecting t his auxiliary to economy. Germany is moving forward towards the same end in other directions, and it is said success h\\s attended the efl'orts of a Dortmund in-ventor in the production of benzol in the coke process.

THE BREWERS' EXHIBITION. THIS annual fixture was opened at the Agricul-

tural Hall, Islington, on Monday last, and seems to be well attended. The principal feature of the show is, as usual, the fine display of coppersmiths' work made by several firms, but these being purely brewery specialities, have little interest for engineers at large.

Gas-engine builders seem to have a special liking for this exhibition, and in addition to Messrs. Crossley Brothers and the Campbell Gas Engine Company, whose exhibits in the same hall we described quite recently in our account of the Laundry Exhibition (ENGINEERING, September 22), Messrs. Tangyes, Limited, of Birmingham, the Griffin Engineering Company, and Messrs. J. E. H. Andrews and Co., have all stands in the present show. The smallest gas engine present is to be found at the stand of the Griffin Engineering Com-pany. This is iutended as a domestjc ~otor, a?d is rated at l horse-power. It has a cylmder 2f In. in diameter by 5 in. stroke, and runs at 350 revo-lutions per minute. On the same stand is also shown a 3 horse-power Griffin gas engine, and an oil engine of similar capacity. Photographs of a single-cylinder gas engine of 300 horse-power are also shown here, and are of interest, as this is the largest gas motor yet attempted. A small arc lamp taking only 2 amperes of cur rent is run off a dynamo driven by the small gas engine~ This lamp is known as the Pell~t lamp, and ~s .exhibited by ~he .A kester Electric Syndicate Limlted, of GranVIlle House, Arundel