290 



NATURE 



[July 30, 1903 



this he deduces the law of Dalton and Gay Lussac, 

 and he further establishes, though in an incomplete 

 manner, the law that in mixed gases the mean kinetic 

 energy is the same for the different sets of molecules 

 present, from which Avogadro's law and Graham's 

 law of diffusion follow at once. The memoir also 

 contains the first calculation of molecular velocity, and 

 points out the relation of this velocity to the velocity 

 of sound. 



The papers on the relative densities of hydrogen 

 and oxygen find a fitting sequel in some of the earlier 

 papers of the fourth volume, the first of which is on 

 the density of nitrogen, Article 197. This begins : — 



" I am much puzzled by some recent results as to 

 the density of nitrogen, and shall be obliged if any of 

 your chemical readers "^ — the article is a letter to this 

 Journal, Nature, vol. xlvi. pp. 512, 513, 1892 — " can 

 offer suggestions as to the cause. According to two 

 methods of preparation I obtain quite distinct 'values. 

 The relative difference, amounting to about i/iooo 

 part 1 is small in itself, but it lies entirely outside the 

 errors of experiment, and can only be attributed to 

 a variation in the character of the gas." 



And the paper concludes : — 



'' Is it possible that the difference is independent 

 of impurity, the nitrogen being to some extent in a 

 different (dissociated) state? " 



The matter is again referred to in the Royal Society 

 paper. No. 201, on the density of the principal gases, 

 published in the Proceedings of 1893, and in detail 

 in Article 210. On an anomaly encountered in deter- 

 minations of the density of nitrogen gas {Proc. Roy. 

 Soc, 1894), when it appeared that while the weight of 

 nitrogen derived from the air required to fill a certain 

 globe under standard conditions was 2.3102 grammes, 

 when the nitrogen was obtained as a chemical product 

 from other sources than the air the weight was 2.2990 

 grammes, a difference of 11 milligrammes, or one- 

 half per cent. The question was answered satisfac- 

 torily by the paper which appears as No. 214, " Argon, 

 a New Constituent of the Atmosphere," by Lord Ray- 

 leigh, Sec.R.S., and Prof. William Ramsay, F.R.S. 

 {Phil. Trans., clxxxvi., A, 1895), and an interesting 

 account of the discovery is contained in the Royal 

 Institution lecture on argon, which forms Article 215. 



The Phil. Trans, paper contains the account of the 

 means used to separate from the nitrogen of the air 

 the new dense gas the presence of which Lord Ray- 

 leigh had discovered, as a residual, by the accuracy of 

 his weighings. 



A number of further papers dealing with argon and 

 some of the other new gases are contained in this 

 volume. One of the latest is on the verification of 

 Boyle's law for low pressures. There is also much 

 valuable optical work, specially, perhaps, Article 198, 

 on the intensity of light reflected from water and 

 mercury at nearly perpendicular incidence, and many 

 important investigations of a mathematical character 

 on the electromagnetic theory of light. Among these 

 may be noted Article 227, on the passage of waves 

 through apertures in plane screens, and Article 230, 

 on the incidence of aerial and electric waves on small 

 obstacles. 



1 The differen e ultimately found was 1/200. 



NO. 1761, VOL. 68] 



Perhaps enough has been written to convey to 

 readers who are not professed students of physics the 

 width of range and the power of Lord Rayleigh's 

 work, and to unite them with those who look to him 

 as their leader and master in thanking him for collect- 

 ing his papers in these four volumes, and rendering 

 them accessible to all. 



It is almost needless to add that the University Press 

 has done its part admirably, and fully deserves the 

 thanks of students of nature for its share in the 

 work. 



Within a few years the Cambridge Press has pub- 

 lished the collected works of Adams, Cayley, Maxwell, 

 Stokes, Tait, Kelvin, Reynolds, and Rayleigh, men 

 whose names will ever make the Cambridge school 

 of mathematics and physics of the last half of the 

 nineteenth century famous in the history of science. 



MICRO-ORGANISMS IN THE ARTS AND 

 MANUFACTURES. 



Technical Mycology : the Utilisation of Micro- 

 organisms in the Arts and Manufactures. By Dr. 

 Lafar. Translated by C. T. C. Salter. Vol. ii. 

 Eumycetic Fermentation, Part i. Pp. viii+189. 

 (London : C. Griffin and Co., Ltd., 1903.) 



THE first volume of Mr. Salter's translation of Dr. 

 Lafar 's " Technical Mycology," which made its 

 appearance some four or five years ago, opened up 

 to the general reader a very wide and interesting field, 

 the utilisation of micro-organisms in the arts and 

 manufactures. This volume dealt with schizomycetic 

 fermentation, and to the uninitiated who had not 

 looked into the scheme of the whole work, it appeared 

 as though almost the last word must have been said 

 on fungi and fermentation. 



The first part of the second volume, the advent of 

 which has been eagerly awaited, has now come to 

 hand, and we may say at once that in many ways it 

 is equal to the first volume and that, not only have 

 we the results of the author's own experience and 

 observations, but a rdsumd of the results of others well 

 brought up to date. This volume deals . with the 

 eumycetic fermentation and opens with a series of 

 chapters on the rudiments of the general morphology 

 and physiology of the Eumycetes, chapters of as great 

 interest to the general biologist as to the bacteriologist 

 and fungologist. A short description of the structure 

 of the Eumycetes is given, the method of spore form- 

 ation, the development of the mycelium from the spore, 

 the gemmating mycelium, and the various methods of 

 reproduction — fructification by sporangia, zygospores, 

 conidia, or by the formation of oidia and gemmae 

 without the intervention of conidiophores. The 

 author refers the reader for more detailed accounts 

 of structure and function to the early text-books pro- 

 vided by Zopf, De Bary, and Brefeld, but supplements 

 these works by carefully written chapters on certain 

 parts of the subject on which much work has been 

 done since the appearance of these text-books. He 

 describes the researches which have been carried out 

 on the celluloses, chitin, hemicelluloses, and other 

 carbohydrates of which these fungi are composed, dis- 



