CIORRESPONDENCE AND NOTES. 123

Should you think such an instrument of any value as a light measurer or worthy of employment at meteorological stations, I shall feel obliged by any criticisms you may be pleased to make.

Yours truly, THOS. B. JORDAN.

Winnipeg,” Cherry Orchard, Staines. * March 20th, 1889.

RAIN FROM A CLOUDLESS SKY (“ SEREIN ”) AT STEVENAGE, JULY 22ND, 1888. By SAMUEL JONES. (Extract from a letter to Mr. J. Bailey Denton.)

‘‘ I beg to submit to your notice certain phenomena observed by me at Steven- age, on Sunday, July 22nd, 1838, about an hour and a half before the approach of a violent thunderstorm. I was standing in the court-yard of my dwelling and talking with a friend who was a farmer ; the weather being then a rather ticklish question with him. I observed what appeared to be the commencement of a shower, and I asked him if it did not rain, to which he said ‘No.’ W e continued the conversation for about the,space of five minutes, when he suddenly broke it off by ejaculating ‘ I t does rain. I said ‘HOW can that be when there are no clouds? I knew the appearance was of an unusual character, and my question and answer were directed with the view of leaving him an unconscious witness of the cause of it, so that he might give his testimony unbiassed by any- thing I might have said.

“The appearance was first seen about 7 p.m., and it looked Iike a shower of luminous particles of a somewhat skim-milky appearance. As soon as I realised the fact of its electrical nature I endeavoured to ascertain if the movement of the particles was upwards or downwards, but without effect. But what I did more successfully observe was that the particles were of the size of tare-seed, and that they moved in remarkabl straight lines, so much so that the resembled the warp in a weaver’s frame. &y view extended over about two-ifthe of the circle of the heavens, and the appearance within that area was precisely the same. My observation lasted s quarter of an hour. The sky was cloudless but hazy looking to the North-west. The subsequent storm came in that direction, being very severe at Sandy.”

NOTE ON THE FREQUENCY OF LONDON FOG. By ALEXANDER B. MACDOWALL. THE phenomenon of fog has been studied a good deal of late ; but apparently little attention has been given as yet to the matter here proposed, viz. the com- parative amount of fog (in London) in recent successive years, and in the winter months, regarded separately.

I n the daily remarks on weather a t Greenwich, as given in the Registrur- GeneraZ’s Weekly Return, may be found a means of measurement (no doubt rough) of this frequency. I have lately gone through these records for the periods Novem- ber to March (inclusive) in the 31 years 1858,,-1888 : the method being to count the number of days on which the word “fog or “foggy ” occur in the reports. No notice is taken of the distinction “ slight fog” or “ dense fog ”; the mere fact of “fog” being considered. Neither ‘‘ mist” nor I‘ haze” is taken into account.

Adding together the number of days on which fog was thus observed in each winter season, we get a series of figures rough1 measuring the fogginess. The yearly average for the whole series is about 26 lays ; or about 5 days in each of the 5 months considered.

The monthly totals are given in the accompanying Table. The most foggy winter in this series seems to have been 1879 (i.e. 1879-80) ;

and the least foggy 1876. Relative maxima also occurred in 1867, 1872, -1886, and relative minims in 1863, 1868,1884 and 1887.

I am unable to throw any light on the cause of those fluctuations. W e might be inclined to think that the most foggy winters would coincide NEW SERIES.-VOL. XV. X