134 



SCIENCE-GOSSIP. 



[June 1, 1S6G. 



CHEMISTRY AND NATURAL 

 PHILOSOPHY. 



CAUSE op the Absorption of Light by the 

 Atmosphere and op the Colour op the 

 Sky. — According to observations by Mr. J. P.Cooke, 

 jun., a very large number of the more faint dark 

 lines of the solar spectrum, hitherto known simply 

 as air-lines, are due solely to the aqueous vapour in 

 the atmosphere. Erom this it results that the ab- 

 sorption of the luminous solar rays by the atmosphere 

 is, chiefly at least, owing to the aqueous vapour 

 which it contains. Erom observations with his 

 spectroscope of the atmosphere of Cambridge, Mas- 

 sachusetts, he has found that these air-lines increase 

 in number and intensity with the increase in the 

 quantity of aqueous vapour in the atmosphere. The 

 absorption of the luminous rays of the sun by the 

 earth's atmosphere, which is estimated by Pouillet 

 to occur to the extent of a third of the whole passing 

 into it, seems therefore, according to Mr. J. P 

 Cooke's observations, to be clue to the aqueous 

 vapour in the atmosphere. The aqueous lines of the 

 spectrum are almost entirely confined to the yellow 

 and red regions of the spectrum, from which it 

 follows that few or none of the blue rays of light are 

 absorbed. The necessary consequence of this is the 

 blue colour of the sky. The setting down the colour 

 of the sky to the absorbent action of aqueous vapour 

 in the air upon the red and yellow rays is in accor- 

 dance with the fact of familiar observation, that the 

 blueness of the sky is much more intense with the 

 moist air of summer than it is with the dry air of 

 winter. 



Is there Ozone in TnE Atmosphebe ?— Many 

 of our readers have performed the experiment by 

 which ozone is said to be detected in the atmosphere, 

 namely, that of exposing to the air a slip of test- 

 paper made active by a mixture of starch and iodide 

 of potassium, and observing if it acquires any colour. 

 Now the evidence afforded by this test has been very 

 justly questioned by Admiral Berigny and M. Eremy, 

 as there are other substances which occur in the 

 atmosphere capable of affecting the ordinary ozone 

 test-papers, and as great irregularity is observed in 

 the results obtained by the use of these papers. M. 

 Houzeau, however, who employs a different kind of 

 test-paper, and one not open to most of the objec- 

 tions which are brought against the ordinary papers 

 of Schoenbcin, seems to have established the exist- 

 ence of an ozonc-likc body, and he has further ob- 

 tained, by condensing the vapours of the atmosphere, 

 an aqueous liquid having all the properties of 

 oxygenated water. He finds that ozone is always 

 present in the atmosphere in both town and country, 

 and that it is principally formed during the occur- 

 rence of storms, hurricanes, and waterspouts, which 

 influence the ozone indications at distances where 

 their existence even remains unknown. D. 



MICROSCOPY. 



Collecting Ground.— Amongst the numerous 

 readers of " Science-Gossip," I daresay there are 

 many who have not opportunity to make long ex- 

 cursions into the country in search of microscopic 

 objects. Eor the information of such, permit me to 

 say, that there are localities in the suburbs of London 

 capable of being reached by a railway trip of a few 

 minutes, and for the trifling cost of a few pence, 

 which during the summer months would well repay 

 a visit. The small pools on Hampstead Heath, 

 for instance, abound with that interesting and beau- 

 tiful object conochilus, also brachionus pala, and 

 other varieties of Rotatoria, together with volvox 

 globator, and several kinds of desmidiacese. In the 

 well-known Hampstead ponds clwra nitellus, re- 

 markable for the facilities it affords of observing sap 

 circulation, grows in abundance. Another locality 

 worth notice is the common at New Wandsworth ; 

 the ponds here, formed from old gravel-pit excava- 

 tions, are teeming with small life. A few weeks 

 since a friend and I took a fourpenny return ticket 

 from Victoria Station to Clapham Junction, from 

 thence a quarter of an hour's walk brought us to the 

 Common. ¥e commenced operations at the pond 

 almost adjoining the enclosure, where once stood 

 the tower built for Rev. Mr. Craig's large telescope, 

 of which nothing now remains but its rusty tube, 

 rotting amidst dirt and rank weeds : here we found 

 large quantities of volvox, red and green hydra, 

 almost every description of fresh-water entomos- 

 traca. the smaller kind of caddis- worm, .whose beauti- 

 fully constructed cases, built up of the minutest par- 

 ticles of sand and dirt, and cemented with inimitable 

 skill and precision, defy the powers of our first-class 

 masons to imitate ; and a large variety of aquatic 

 larva 3 ., amongst which was that favourite of the micro- 

 scopistthe transparent larvseof a small kind of gnat, 

 and that Dahomean savage of the waters the larvae of 

 the dytiscus, valuable for its fine development of 

 the tracheal process. In a ditch close by, running 

 at the end of several cottage gardens, we collected 

 fine clostcrium, showing the circulation with a ^-inch 

 objective, Micrasterias and other desmids. In con- 

 clusion I may say, New Wandsworth Common is a 

 favorite spot with me ; it was here, in a large piece 

 of water near to the railway station known as the 

 " Black Sea," I first discovered, after years of search 

 in other directions, that rare and exquisite polyzoar 

 Cristatclla muecdo ; and from another large pond 

 skirting the road and opposite the cemetery, I ob- 

 tained the equally rare and interesting member of 

 the same family, Cristalina lophophus — /. S. 



Plant Circulation. — A cyclosis, or circulation 

 of protoplasm, may be very easily seen in the fine 

 rootlets of the common water-weed known by the 

 name of " Frog-bit." A power of from 250 to 300 

 diameters shows the circulation well. — /. /. R. 



