64 



NATURE 



[May 19, 1887 



lished by Herr B. Herder, of Freiburg-im-Breisgau. The pre- 

 sent volume contains a clear and popular account of the work 

 done in each of the sciences in the year 1886. 



We understand that the second part of the "Manual of 

 Practical Botany," by Prof. Bower and Dr. Sydney Vines, will 

 be published by Messrs. Macmillan and Co. in the course of a 

 few weeks. It will include the Bryophyta and the Thallophyta ; 

 among the chief types, used being Polytrichum commune, Mar- 

 ehantia polymorpha, Polysiphonia fastigiata, Fucus serratus, 

 Coleochate scutata, Volvox globator, Agaricm campestris, 

 Claviceps purpurea, Eurotium Aspergillus, Pythium de Bary- 

 anum, and Mucor mucedo. Besides these a good many 

 subsidiary types are used to illustrate special points. 



" A Classification of Animals," drawn up by Mr. E. T. 

 Newton for Mr. H. B. Woodward's "Geology of England 

 and Wales," has now been issued separately. It is founded on 

 the classifications proposed by Prof, Huxley, with such modifica- 

 tions as are, in the author's opinion, rendered necessary by recent 

 discoveries. 



The Annual Report of the Royal Alfred Observatory, 

 Mauritius, for the year 1885, has been issued. The mean 

 temperature for the year at the Observatory was 73° -6. The 

 highest reading was 86° 7 in February, and the lowest 5 7° -4 in 

 July. Rain fell on 200 days, and amounted to 44 "61 inches ; 

 the fall was below the average in the usually wet months of 

 January to April, but above the average in the usually dry 

 months of May to October. The island has not been visited by 

 a hurricane since March 1879, although several cyclones have 

 passed not far from it. The Report contains observations made at 

 various stations in the island and at the Seychelles, and notices of 

 storms in the Indian Ocean, collected from ships' logs. Photo- 

 graphs of the sun were also taken daily, when the weather per- 

 mitted. There were 354 days on which it is certain that spots 

 were on the sun's disk, and eight days on which it is certain that 

 there were none. The number of spots in May was unusually 

 great. 



In a recent book, " L'Enseignement actuel de I'Hygiene 

 dans les Facultes de Medecine en Europe," Prof. Loewenthal, of 

 Lausanne, shows that the time allowed per year for the teaching 

 of hygiene varies from 20 iiiinutes per week in England to 9 hours 

 per week in Spain. The other countries range between these 

 two extremes. The average is from 2 J to 3 hours i^er week for 

 the whole year. 



In the May number of the American Journal of Science will 

 be found a paper by Mr. Carey Lee, of Philadelphia, in which 

 are described a remarkable series of salts of silver, which the 

 author is attempting to make use of in obtaining photographs of 

 objects in their natural colours. It is first shown, by an ex- 

 haustive series of experiments, that when light acts upon ordin- 

 ary silver chloride, AgCl, in presence of hydrochloric acid, the 

 darkening is due to the formation of a small quantity of sub- 

 chloride, AgjCl, which enters into combination with the un- 

 altered silver chloride to form a reddish compound of a nature 

 similar to that of a " lake." This red chloride of silver is termed 

 protochloride, and is found to be, unlike subchloride, unattacked 

 by cold strong nitric acid. After a certain amount of this sub- 

 stance is formed, the action of light appears to cease — a pheno- 

 menon which has been frequently noted by other observers. 

 Successful efforts were then made to prepare protochlorides, 

 bromides, and iodides of this nature, and a full description of the 

 very numerous methods and analyses is given in the memoir. 

 The startling fact was discovered that all varieties of tints from one 

 end of the spectrum to the other could be obtained under suitable 

 conditions. Normally, the protochloride of silver is red, even 

 one-half per cent, giving to ordinary silver chloride a strong 



coloration ; but on exposure to diffused sunlight it quickly 

 changes to purple. On addition of mercuric chloride it becomes 

 gray, potassium bromide changes it to a permanent lilac, potas- 

 sium iodide to a bluish tint, while a mixture of potassium chlorate 

 and hydrochloric acid causes it to pass through pink and flesh- 

 colour to pure white. Heat, on the contrary, causes it to retake 

 its red coloration, and on exposure to various parts of the spec- 

 trum it affects lovely", shades of the most varied hues. The 

 important observation was made that, in presence of small 

 quantities of lead or zinc chloride, white light (which darkens 

 the pure protochloride) bleaches it, thus producing white in those 

 portions of the image which ought to be white ; and it was also 

 found that the addition of a little sodium salicylate enhances the 

 sensitiveness threefold. The experiments are being continued, 

 and appear likely to lead to important results in chromo- 

 photography. 



The current number of the Auk (vol. iv. Part 2) contains 

 some interesting papers, but none of great importance. The 

 want of finality in the system of nomenclature now practised 

 by the American ornithologists is as marked as ever. Thus, 

 Dr. Stejneger, having previously settled the synonymy of the 

 redpolls, by the confounding of all received nomenclature, and 

 the introduction of nine new synonyms into the already over- 

 burdened literature of six species, here furnishes a tenth hitherto 

 unrecorded title for our British redpoll ; and Mr. Brewster fol- 

 lows suit by adding another synonym to one of the American 

 species of the same group. It might be well for ornithologists 

 to consider whether the best plan would not be, as Mr. Seebohm 

 advises, to simplify matters by accepting in every case the name 

 that happens to have been for a long time most in vogue. 



In an interesting paper on the Ailsa Craig Lighthouse, read 

 lately before the Scottish Institution of Engineers and Ship- 

 builders, Mr. G. M. Hunter drew attention to the admir- 

 able system of illumination and signalling in the Firth of 

 Clyde. There are Corsewall Point light, alternating white and 

 red, at the entrance to Loch Ryan, distant from the Craig 17 

 miles ; Sanda Isle light, off the Mull of Kintyre, distant 18 miles ; 

 Turnberry light, off the Ayrshire coast, distant 12 miles ; Pladda 

 light and fog-signals, off the southern end of Arran, distant 12 

 miles ; and Holy Isle green and red light, distant 18 miles— all 

 of which are revolving lights, with the exception of the fixed 

 lights at Pladda and Holy Isle. These lights are all under 

 ordinary circumstances visible from Ailsa Craig. 



In the Izvestia of the Russian Geographical Society there are 

 some interesting remarks, by A. N. Krasnoff, on the history of 

 the valley of the Hi River in Russian Turkestan. The Russian 

 traveller considers that during the post-Pliocene age the 

 valley of the Hi was nearly all occupied by water, and that the 

 vegetation on the shores of this basin was quite different from 

 that which exists now. It resembled, he thinks, the present 

 vegetation of Middle Russia. There were forests of deciduous 

 trees, among which maples, elm-trees, and apple-trees prevailed, 

 and black-earth steppes occupied wide areas. Relics of this 

 vegetation survive only at the foot of the snow-clad mountains, 

 where they find the necessary moisture. Several of the species 

 have there undergone remarkable adaptations, which permit then 

 to support the rigorous continental climate. Deprived of the 

 moisture of the snow-clad peaks, the vegetation of the lowei 

 ridges has completely changed since the recent desiccation 

 those parts of Asia. These ridges are covered now with £ 

 purely Central-Asiatic flora. As to the shores of Lake Bal 

 khash and Ala-kul, they are either stony deserts with smallgrass} 

 plants, or shifting sands covered with the characteristic Aral 

 Caspian bushes nearly destitute of leaves. The Balkhash wa: 

 formerly a much greater lake than it is now, and it is rapidl] 

 becoming smaller. The depth of the Ala-kul Gulf has so fa 



