514 



NATURE 



[September 29, 1892 



water. The odd circumstance about the damage was that it 

 occurred on a simple grass slope, about half way between a tall 

 boat-house on the one side and a drinking fountain standing on 

 more elevated ground on the other. Small trees also were in 

 the neighbourhood, and there was no apparent cause why the 

 flash should have selected this particular spot ; though indeed 

 it was not within any of the ordinarily accepted "areas of 

 protection." A gentleman — Mr. Hewitt — proposed digging for 

 the meteor, and although fairly convinced that it was nothing 

 but an ordinary flash, we thought it just possible that an acci- 

 dental meteorite might have fallen during the thunderstorm ; in 

 which event a flash down the rarefied air of its trail would be a 

 natural consequence. It may be just possible that the popular 

 belief in thunderbolts has some such foundation. 



At any rate the excavation was made, with the result of 

 proving that it was an ordinary flash and that the lightning made 

 use of a surface drain-pipe, about four feet deep, to get at the 

 water of the lake. 



I enclose Mr. Hewitt's report. Oliver J. Lodge. 



During a thunderstorm on the afternoon of Sunday, July 3, 

 1892, what is described as a " ball of fire" was seen by several 

 persons to descend to the ground, near the south end of the Fake 

 in Sefton Park ; and immediately afterwards a column of water, 

 about sixty feet high, was shot up from the lake. On examining 

 the spot where the ball of fire was seen to descend, several clean- 

 cut holes were observed, and a sod was also found at a little dis- 

 tan ce from the spot. 



A few days afterwards an excavation was carefully made. 

 The sod being removed, the holes were traced down to a surface 

 drain pipe four feet below the surface. At this drain the holes 

 terminated, and the pipe was found shattered. The important 

 holes were found to be six, the largest being seven inches in 

 diameter, the others about two inches. No meteoric matter was 

 found, but it seems curious that this effect wasjbrought about by 

 a flash of lightning only, in an open space of sloping grass, 

 when there were trees and houses close by. 



Aigburth, Liverpool. George H. Hewitt. 



Peripatus Re-discovered in Jamaica. 



Mrs. E. M. Swainson has been so fortunate as to find on 

 Beacon Hill, near Bath, three specimens of Peripatus, which she 

 has sent to the Institute of Jamaica. The species is doubtless 

 identical with that found by Gosse many years ago at the other 

 end of the island. Of the two specimens which we have 

 studied, one has 36 pairs of legs, and is dark pinkish-brown, 

 with the ends of the antennae pure white, in striking contrast ; 

 the other is smaller and darker, without white ends to the an- 

 tennae, and with only 29 pairs of legs. The third example, 

 which we have still alive, is larger, but dark in colour. Full 

 details will be given elsewhere later on, and it may suffice for 

 the present to state that the species is very closely allied to P. 

 Edwardsii from Venezuela, as described by Sedgwick, but differs 

 in the greater number of legs and the white-tipped antennae of 

 certain individuals (probably the females), in the only slightly 

 curved (not hooked) claws, in the differentiation of the papillse 

 into two distinct kinds on the dorsal surface, and apparently in 

 other minor matters. There is no dark dorsal line. The genital 

 orifice is between the penultimate pair of legs ; and the jaws are 

 almost precisely as in Edwardsii. The Jamaican species being 

 e vidently new, it is proposed to call it Peripattis jainaicensis. 

 M. Grabham. 



September 5. T. D. A. Cocker ell. 



Reflection on Valley Fog. 



A letter from an observer at the Lick Observatory appeared 

 in Nature on August 25, reporting the reflection of mountains 

 in a valley fog. I was therefore much interested to note the 

 following in the Yorkshire Herald of September 7 : — 



"Sir, — Possibly it may interest your readers to hear of a 

 natural phenomenon I noticed this morning before 6 a.m. 

 Overlooking, from Leyburn, the valley of Wensleydale, it ap- 

 peared as though more than half of the dale was filled with 

 water, like a great lake with rising hills on either side, and 

 these hill-sides, above the level of the (apparent) flood, were 

 distinctly reflected in it. The sun was shining brightly at the 

 time, but almost immediately the mist began to disperse, and 

 the mirage faded away. What struck me as unusual was the 



NO. I J 96, VOL. 46] 



extraordinary distinctness of the reflection. Yours, An Early 

 Riser, September 5, 1892." 



In both cases the reflecting film seems to have been near its 

 vanishing point. J. Edmund Clark. 



Impure Water in Bread. 



Some accurate answers to the following questions would be 

 desirable, in view of public health. 



(i) What bacilli — if any — can survive in the amount and 

 duration of the heat of baking in the interior of unfermented 

 bread ? 



(2) What is the further effect of the carbonic acid of fermen- 

 tation ? 



(3) What is the effect of the water being highly carbonated 

 without fermentation, as in aerated bread ? 



W. M. F. P. 



The Comets of Brorsen (1846 VII.) and Brooks 

 (1892 • V). 



The elements of Brooks's comet " 1892 d," as computed by 

 Berberich from four observations made between August 31 and 

 September 5, bear a strong resemblance to those of Brorsen's 

 comet of 1846, calculated by Oudemans, the figures being — 



Comet Comet 



Brorsen (1846 VII,) Brooks (1892 ^) 



T ... 1846 June 5'479 ... 1892 Dec. 19727 



a> ... 260 12 50 ... 269 24 27 



a ... 261 53 12 ... 261 2 55 



i ... 29 18 47 ••• 27 57 8 



Log q ... 9-80188 ... 9-84455 



Brorsen's comet of 1846 was visible to the naked eye on May 

 14 of that year. It was supposed to be revolving in an elliptical 

 orbit, with a period of about 400 years. W. F. Denning. 



Bristol, September 22. 



NOTE ON THE PROGRESS OF THE DIOPTRIC 

 LENS AS USED IN LIGHTHOUSE ILLU- 

 MINATION. 



ipRESNEL, in 1820, devised and constructed a lens 

 -*- for first order lights of 920 mm. radius. It was 

 composedof aplano-convex lens, with five refracting prisms 

 concentric with it, and four segments of rings in the corners 

 all gradually decreasing in breadth as they receded from 

 the centre. The separate pieces of which these lenses 

 were made up were cemented together and mounted in 

 metallic frames 30 inches square. 



In 1835, the late Mr. Alan Stevenson introduced the 

 French apparatus into Great Britain. In doing so he 

 made several improvements, one of which was that he 

 increased the height of the lens from 30 to 39 inches, at 

 the same time diminishing the thickness of the glass. This 

 refractor had eight prisms above and eight prisms below 

 the central lens. From that time Alan Stevenson's lens 

 was almost universally used until a comparatively recent 

 date, when a revolution in the size of lenses took place. 



A few years ago inventors were trying to obtain greater 

 power by increasing the diameter and volume of the 

 flames ; but Messrs. Stevenson pointed out, in 1869, that 

 after a certain point an increase of diameter of the lumi- 

 nary not accompanied by a corresponding increase of the 

 radius of the apparatus was a mistake, as the light be- 

 came ex-focal and divergent, and that the proper way to 

 secure greater power was to enlarge the diameter- of the 

 apparatus. In 1885 they had a lens made to their design 

 of 1330 mm. radius, and having a height of 5 feet. This 

 lens, which was named " Hyper-radiant," was tried at 

 the South Foreland against other lenses, and with a large 

 lo-ring gas burner it was found to give a light from one 

 and a half to twice as intense as the ordinary lenses 

 which were pitted against it, with the same large burners 

 in their foci, thus proving conclusively that to get the 

 power out of large burners it was imperatively necesiary 



