♦ KNOWLEDGE ♦ 



[JCLY 4, 1884. 



PHOTOGRAPHING A FLASH OF 

 LIGHTNING. 



THE accompanying engraving was made directly from 

 a iihotoLjraph sent to us by Mr. W. C. Gurley, of 

 Marietta Observatory, who writes as follows : — 



" The reproduction of a flash of lightning by photography 

 would, a few years since, have been deemed quite an impos- 

 sibility, but the introduction of the rapid bromo-gelatine 

 process has rendered it not only possible but comparatively 

 easy of accomplishment. 



" The accompanying photograph is from a negative taken 

 by myself during a thunderstorm which passed several 

 miles south of the observatory on the evening of May 4. 



" Wheatstone has demonstrated by direct experiment that 

 the duration of a single flash of lightning cannot possibly 

 exceed a millionth of a second. That a photograph showing 

 the detail of the one mentioned could be taken in this in- 

 appreciably short time seems quite wonderful, not to say 

 incredible. The plate employed was one of Cramer's extra 

 rapid, and developed with strong pyrogallic developer. 



" It will be observed that the flash is not of the usually 

 depicted zigzag form, and that it seems to be alteroately 

 contracted and expanded in its passage through the 

 atmosphere. 



" Taking the interval between the flash and the report, I 

 estimated its distance from the camera to have been about 

 five miles." — Scientific American. 



The report ou the composition and quality of daily samples of 

 the water supplied to London, for the month ending May 31st, 

 1884, by William Crookes, F.K.S., William Odling, II.B,, F.R.S., 

 F.R.C.P., and C. Meymott Tidy, M.B., F.C.S., says:— "Of these 

 189 samples of water, the whole were, without exception, clear, 

 bright, and well filtered. The quality of the water supplied to the 

 metropolis during the past month, as indicated by its state of 

 aeration, and high degree of freedom from colour and excess of 

 organic matter, was excellent. Its perfect filtration was shown by 

 the absence of even a trace of suspended matter in any one of the 

 numerous samples submitted to examination." 



THE ANTARCTIC REGIONS. 

 Br RicHAKD A. Proctor. 



THERE are parts of our earth of which we know less 

 than of the moon, or even of some of the planets. 

 The eyes of the astronomer have looked upon the unattain- 

 able .summits of the lunar mountain.^ : he has studied the 

 arid wastes which lie within the lunar craters ; he has 

 mfasured the light which these regions reflect — nay, even 

 to the degree to which they are warmed under the blazing 

 sun of the long lunar day. Passing beyond the moon, the 

 astronomer has studied the lands and seas of a world 

 which has justly been termed a miniature of our earth : he 

 has watched the clouds which form over the continents and 

 oceans of the planet Mars, and are dissipated even like our 

 own by the solar rays ; he has determined the very con- 

 stituents of that planet's atmosphere. But more than this, 

 the astronomer has actually studied the condition of parts 

 of Mars, where (if analogy can be trusted) the very inha- 

 bitants of that world are unable to penetrate. The ruddy 

 orl) which during the spring months was now conspicuous 

 in our skies presents to the astronomer its Arctic and 

 Antarctic wastes. He is able to watch the gradual increase 

 of either region as winter prevails alternately over the 

 northern and southern hemisphere of Mars ; he can measure 

 their gradual reduction with the progress of the Martial 

 summer ; aud he can infer from their aspect that even 

 in the height of summer there still remain ice-covered 

 regions so wide in their range as doubtless to defy the 

 eflbrts of the Martialists to penetrate to the poles of the 

 globe ou which they li\e. So that where most probaljly no 

 living creature on Mars has ever penetrated, the astronomer 

 can direct his survey ; and questions which no Maitial 

 geographer can pretend to answer the terre-strial astronomer 

 can discuss with a considerable degree of confidence. It is 

 the same even with the more distant planets Jupiter and 

 Saturn. Despite the vast spaces which separate us from 

 these orbs, we yet know much respecting their physical 

 habitvides ; and whereas our knowledge of our own earth 

 is limited by certain barriers as yet unpassed, and probably 

 impassable, there is no pait of the surface of either of the 

 giant planets which has not come under the astronomer's 

 scrutiny. 



These considerations suggest in turn the strange 

 thought that possibly the unattained places of our 

 earth have been viewed by beings which are not of this 

 world. I say possibly, but I might almost say j^'^^'- 

 hahhj. It seems in no degree unreasonable to sup- 

 pose not merely that the earth's sister-planet Venus is 

 inhabited, but that some creatures on Venus possess 

 the reasoning powers and the insight into the secrets of 

 Nature which have enabled the inhabitants of Earth 

 to study the orbs which circle like herself around the 

 sun. If this be the case— if there are telescopists in 

 Venus as skilful as those inhabiting our earth — they 

 are able to answer questions which hitherto have baffled 

 our geographers. They may not, indeed, have the 

 means of ascertaining details respecting the structure 

 of our continents and oceans. They cannot know, 

 for instance, whether the region to which Livingstone 

 has penetrated is, as he supposes, the head of the 

 river we terrestrials call the Nile, or, as others suppose, is 

 in reality the head of the Congo. For certainly no tele- 

 scopic powers possessed by our astronomers could give us 

 information on such points, if our position were inter- 

 changed with that of the inhabitants of Venus. But 

 astronomers in Venus can, without excessive telescopic 

 power, inform themselves whether our polar regions are 



