277

ORDINARY MEETING, JULY 7TH, 1871.

Professor MORRIS, F.G.S., H.M.G.A., Vice-President, in theChair.

The following Donations were announced :-

"Journal of the Quekett Microscopical Club," from that Club."Abstract of Proceedings of the Geological Society," from that

Society."The Thirty-Seventh Annual Report of the Royal Cornwall Poly­

technic Society for 1869," from that Society."The Thirty-Eighth Annual Report of the Royal Cornwall Poly­

technic Society for 1870," from that Society.

The following were elected Members of the Association :-John Gould Avery, Esq., M.A. I. ; John Barber, Esq.; William

Bartlett, Esq., F.R.C.S.; Ralph Augustus Busby, Esq.; Lieut.«Col. Capel Coape j Henry Monk, Esq. j George Staley Mosse,Esq. j John E. L. Shadwell, Esq., M.A. j George William Spaw­forth, Esq. j and Mrs. Peter Taylor.

The following Papers were read:-

1. ON THE UPPER LIMITS OF THE DEVONIAN SYSTEM.

By S. R. PATTISON, Esq., F.G.S.

I am not about to revive the controversy in which the latelamented Mr. Jukes maintained with distinguished gallantry for somany years that the Upper Devonian had no existence. Thisdispute is settled. Devonian has conquered. The careful work ofMr. Etheridge, crowning the labours of a band of distinguishedDevonians, has demonstrated that the Devonian System is a greattriple natural history division. It was dragged out of the ocean ofGrauwacke in 1836, after having been seen by Mr. Lonsdale, heldup to public view by Sedgwick and Murchison, at the BritishAssociation of that year, and has duly passed into the literature ofContinental and American geology.

I have a few words to say this evening on the district in whichit was first determined.

Referring you, then, to North Devon, and reminding you thatthe opening of the new railway from Taunton to Barnstaple willrender the country more accessible than it is at present, I take you

278 B. R. PA TTIS ON ON THE UPPER DEVONIAN.

down by th e old route. From the rich red marl of th e TauntonValley, going south, we first encounter a set of coarse schistosesandstones, the Foreland, extending over the hill to th e picturesquegorge of Lynton; next, and from th ere, a range of rocks, some­what less coarse, including the limestones of Coombc Martin, thethin representation of the great Eifelian, Plymouth, and Torbaycalcareous masses. H ere we have a good horizon, and we call itMiddle Devonian, baving thrown tb e series just passed tbrough,with a southerly dip , into tbe category of a Lower Devonian.The Ilfracomb Series ends upwards in another set of hard sandst ones(Pickwell Down), and upon the se lie an uppermost series of shales,and lumps of limestone s, and gr ey beds, extending to the base ofthe carbonaceous rocks, and these we term Upper Devonian. Thanksto the discrimination of the late Mr. Salter, we are at no loss as tothe Upp er Devonian in North Devon. They may be called the"Barnstaple Beds," by way of distinction. They extend fromthe town to th e edge of the carbonaceous series, and th ence outwardto the cliffs at Crouch Bay. Th e section runs thus, in ascendingorder. 1. Purple slate and sand stones. 2. Pale slate with a fewbivalves. 3. Gr ey grit, a thick series. These three form the Mar­wood beds. Then 4, an alternating series of greenish-grey grits, orgrey cleaved slate-the Pilton Beds. 'I'he Upper Devonian is bothstratigraphically and palreontologically here divided into twogroups , the upper, Pilton j the lower, Marwood. The uppermostbeds touch the carbonaceous limestone, which, however, overlapsdifferent beds on its lin e. The Marwood Group is a shallow seaaccumulation; it displays a distinct Devonian fauna. I do nottrouble you with lists of fossils. They will be found admirablyarranged by Mr. Etheridge, but were also well characterised by Mr.Salter. In th e green slat es of this series plants occur. ThePilton Group contains an analogous fauna , sufficiently distinguished.These are th e typical displays of the Upper Devonian. Thisstratigraphy has been well establi shed, and th e fossils render thematter certain. Mr . Salter's memoir, Quart. J ourn. Geo1.Soc.,vol. xix., p. 480, will give all that is needed for the discovery,identification, and collocation of these beds.

If we now resume our progress southward, and cross the wideand dull expanse of lower carbonaceous clays and gri ts, with itsthin fringe of limeston e at th e base, we find a rough basin of theseoverlying rock s, of which the lower or southern edge extends into

S. R. PATTISON ON THE UPPER DEVONIAN. 279

Cornwall, and runs east and west, a little north of Launceston,Emerging from under th ese, finding our latitude by the basementbeds of grit and Carboniferous Limestone with coal plants, we firstencounter a lower limestone with fossils, at South Petherwyn.Sedgwick and Phillips, and also De la Beche, placed these roughlyon a parallel with the Bernstaple Beds. The fossils, they considered,though not identical as a whole, yet had a common facies. Salterdid the same, though he considered them to form a lower group ofthe Upper Devonian, and treated a small intervening inlier nearYeolmbridge as the exa~t parallel of the Barnstaple Beds. If thisbe correct, we have a third series of the Upper Devonian, viz., thelowest, Petherwyn j the middle, Marwood; the uppermost, Pilton.I do not know the Pilton Beds from observation save from one veryshort morning's walk, and should be inclined to place the Pother­wyn and Pilton as synchronous. But this is a matter of littleimportance in a formatiou so notoriously patchy as the UpperDevonian.

If either of these be correct, we have, as wego southwards throughCornwall, and pass over a set of beds having a general dip to thenorth, a triple series like that of North Devon :-the Petherwyn,or an approximate parallel to Barnstaple, Upper Devonian; thePlymouth, undonbted Middle Devonian; the Looe rock, LowerDevoniau; and in addition the Gorran quartzites, Silurian.

But a recent and competent observer exclaims" NOUIJ avons changetout cela;" Dr. Holl, of Malvern, who in his youth explored theseregions, has in his maturer age given them careful revision. Hehas embodied the results in a memoir "On the Older Rocks ofSouth Devon and East Cornwall," Quart. Journ~ Geol. Soc., vol.xxiv., p. 400. After much good work, he conclndes that there isno Upper Devonian in Cornwall, and that the whole series is MiddleDevonian, and thus he alters the received notions concerning agreat part of Cornwall.

Mr. Hell's proposition is that the fossiliferous rocks of SouthPetherwyn have been erroneously assigned to the Upper Devonian,and that, on the contrary, they are Lower Devonian. He adducestwo arguments in support of this. 1. That it is contrary to the actualsection, as the rocks have a general north underlay at Petherwynwhich, travelling southwards, is soon exchanged for a general southunderlay as far as Plymouth, and therefore that the PlymouthMiddle Devonian should come in south of the Petherwyn if this

280 s. R. PATTISON ON THE UPPER DEVONIAN.

latter are Upp er, which they do not , and th erefore th ey are belowth e Plymouth Beds.

But this is by no means conclusive in so broken a country, andwith so spotty a formation as the Upper Devonian. EspeciaUy asth e intervening axis is the great granitic axis of Devon and Corn­wall, which has faulted and disturbed the beds at some dat e subse­quent to th e deposition of th e Carboniferous, and therefore we mayhave any amount of denudation as well as fracture exhibited in theold country. There are therefore five hypotheses, all of them trueeauses which may have prevented this :-1. Thl! great gran iticuplift. 2. Minor faults on the line of strike. 3. Denudationwhich has stripped off much of every bed. 4. Non-continuance ofthe Plymouth in the arch southwards; or 5thly, that the PetherwynBeds are mere local patches in a synclinal trough of the Middle.

Mr. Holl's second reason is that the palreontological evidence ofth eir being Upper Devonian is not conclusive, but capable of beingused for either. Now thi s is a remarkable assumption, as Phillips,Salter, Etheridge, and others, who were fully alive to th e distinction,have written, and spoken, and published otherwise, and that re­peatedly. But of course authority is not argument. There are73 good species found at Petherwyn, deducting th reeduplicates. Mr.Holl, for th e purpose of comparison, first takes off 21 species peculiarto this formation. I demur to this proceeding, unless he gives thefacies of the se, and shows that it differs from that of the depositt o be identified. Amongst the se 21 species which he eliminatesoccur eight ClymeniaJ, a Goniatite, and a Nautilus, all peculiar toP eth erwyn. . Why, for purposes of identification should th ese beleft out? If they have no broth ers elsewhere, th ey have cousins.Th e family likeness of th e 21 does not point downwards into LowerDevonian, but upwards to the continental uppermost Devonian, andeven aspires to th e Carboniferous. The very circumstance whichinduced the Irish Survey to put th em up, leads Mr. Holi to sinkth em down. Then he excludes 10 others not found in BritishDevonian, viz-Cypridina, Pterinea, Cardiola, N atica, and L oxonematumida. The same remonstrance must be offered against this ex­tradition. The comparison becomes incomplete if these are leftout. Noscitur e sociis is good for man and beast, especially withth e Cephalopoda. The palreontologi st gathers his impression fromthe gronp as a whole. On Mr. Hall' s arrangement there are 40species common to Petherwyn and Middle Devonian against 27 com-

True, but th e items omitte dthe difference-the H amlets,

S. R. P ATT ISO N ON TIlE UP P E R DEVOKIAN. 281

mon to P etherwyn and Barnstaple.are precisely th ose which est ablishwhich are the making of th e play.

It would be ted ious, and ind eed improper here, to weary youwith details. Speakin g from the recollection of many years ago,I would characterise the P eth erwyn as a deposit of some half dozenbeds of impure limeston e and slate, characterised by these 73good species, all found in a small space. The beds lire not nowworked for lime, nor are any other quarries opened in them, andhence the opportunity of making fresh investigation is gon e. Avery few shattered and imperfect fo'ssils may be found among thedebris of the old quarries and in the beds along the line ofstrike.

These beds dip under the carbonaceous beds, which are close tothem on the north, and st rike, with the general run of the country,round the base of the granite. Towards Plymouth they are succeededby lower barren sandstones, and the latter support them also on theopposite line of strike, north and north-west.

In trending round a larger development of some of th e PetherwynBeds may be occasionally tr aced to Tintagel, and by Delabole south ­wards to near Bodmin, whilst out side of these and below themoccur at Padstow feeble represent ations of th e Plymouth Series,and lower down, at Newquay, we are on the track of the LowerDevonians of Looe and F owey. The great Eifelian limeston e ofPl ymouth does not come in at all to th e northward, until we cometo th e second great fold at Barn staple. This brings th e whole oftha t broken country into regular sequence, continued by the Silurianquartzites at Gorran, and everywhere on a north and south linecrowned by the Carboniferous.

It will be useful in so rough a country geologically, so ill fitted forrapid conclusions, to inquirewhetber th ere are any analogous featuresin th e Palreozoics elsewhere. Th e, South Devon section I have not.examined, but it is evident th at th e upper portion of the Newtonlim estones, though conformable to the lower, yet introduce a newset of organisms, and in a very thin way represent th e commence­ment of Upper Devonian. Thi s was Mr. Salter's opinion. InP embroke shire, in West Angle Bay, at the base of certain Old RedSandstone beds, lie Carboniferous Slates, and in the lower portio n ofthese, apparently quite conformable, are Upper Devoniana.

In Ireland we have a largely developed series, with some charac-

282 s, R. PATTISON ON THE UPPER DEVONIAN.

ters differing -the Coomhola Grits, comprising both layers of theUpper Devonian., viz.-the Marwood and Pilton Beds.

On the Belgian fronti er of France I have followed the Devonianfrom beyond Givet down the Meuse, and found small traces of any­thing above the Plymouth Limestone of Givet, until coming downto the district bordering the coal basin of Belgium, Then occurthin bands of intennittent limestone and heavy sandstones, calledfirst by Dnmont, "Psammites de Oondros." I was directed tothese by Mons. Gosselet, the accurate and conscientious Pro­fessor and Curator at the Sorbonne. Ncar Avesnes, at Oetrungt,the black Carboniferous Limestone is found in the near neighbour­hood of a grey, thin, many-bedded limestone, which contains Cly­menia. This attracted my notice, and I went to Oetrungt toascertain, if I could, its conditions and relations. I could not makeout all the beds which my friend Gosselet had pictured, but ingeneral the quarry is like a Devonshire limestone quarry, withUpper Devonian types, and even some forms attributed to the Car­boniferous Limestone. I exhibit a section showing the marvellousnumber of beds. Some of the same fossils occur throughout.Generally on the borders of the coal district we have either a greatslaty series, the Famenne, or a thick sandstone with a few lime­stones at the base, or both. The latter are characterised through­out the Belgian and French area by the occurrence of Ter ebratula(Rhynchonella) cuboides.

In the Boulonnais the same thing occurs. I have seen therethe yellow sandstone-Marwood-resting on Eifelian, or MiddleDevonian slates and limestone, the Clymenian or Petherwyn beingwanting.

On the Rhine and in Nassau the Upper Devoniana are in forceand well marked. Here they are not accompanied by the presenceof Carboniferous Limestone. They are the well-known CypridinianSchiefer, characterised by Cypridina serro-striata; found also atPetherwyn. Krammenael-stein, or Ant-stone, Clymenia-kalk, thePetherwyn Group, and th e Verneuilli-schiefer, together constitutingthe Marwood and Pilton Groups, the whole series of the UpperDevoniana. Roemer divides it into 4 (" Siluria," p. 372), thelowest of which is the Rhynchonella cuboides bed of the Frenchfrontier, next the Clymenia-limcstone, and above these the Goniatite­limestone, capped by Receptaculite schists, the whole corres­ponding to our Petherwyn and Barnstaple series. So in West-

CALEB EVANS ON THE LONDON CLAY. 283

phalia there is Clymenia-limestone, and above it two beds com­pared to Marwood and the Pilton, or yellow-sandstone of Ireland.

In North America the Chemung and Portage Groups represent ourUpper Devonian, and are well established j they are there, withoutquestion, held to constitute a good stratigraphical and palreonto­logical division. There is no defined divisional plane between theChemung and the Carboniferous Sandstone (Bigsby), i, e., it isdifficult to make out the division physically; but once in either, andyou recognise the difference, without doubt (Dana, 287).-SeeDawson's picturesque, yet full and careful description in " LeisureHour," May, 1871, p. 296.

From this sketchy review we have no hesitation in affirming theclear division of the Upper Devonian from the Carboniferous as aconvenient natural history and stratigraphical division. The strata.exhibit the sediments of deep sea bays, with occasional swampsand muddy shallows, and prove that this state of things was oflongcontinuance, a kind of premonition of the Carboniferous. A neworder of things was being gradually established, both physicallyand palreontologically, so that it is part of the case that the UpperDevonian .should be the most transient and interrupted portion ofa transition formation, the close of an era, not ending in storms,but in peace and mud.

It is hardly necessary to remind you that our so-called Systemshave two artificial lines, viz., those which affect to separate themfrom the whole, and that it is the space thus artificially separatedfor examination that we call a System. Looked at in anotheraspect they are but parts of a whole; but for convenience weseparate facts into collections and class together those which havegeneral resemblances. The number of these resemblances augmentstowards a maximum by degrees, and descends by degrees; so thatwhilst the culminating line or point of these resemblances may bewell and strongly made out, yet the edges will in the nature ofthings be shadowy and debateable.

2. ON A NEW SECTION OF THE UPPER BED OF THE LONDON CLAY.

By CALEB EVANS, Esq., F.G.S.

(Abstract.)The author drew the attention of the meeting to an exposure of

a very fossiliferous bed of the London Clay, near Ohilds Hill,Hampstead.