January 5, ic,o5] 



NA TURE 



219 



similar occasions. Since 1882 Prof. Onnes has been 

 director of the physical laboratory at the University 

 of Leyden, and the book gives a description of the 

 growth of the institution since his accession to the 

 directorship, of its present condition, and of the work 

 carried out by himself and by his pupils under his 

 supervision. In a sense it is a matter for regret that 

 by the nature of the case he himself had to be excluded 

 from the list of contributors ; on several of the subjects 

 dealt with it would be interesting to have the director's 

 personal views. 



After an eloquent dedication from the hand of Prof. 

 Bosscha, we find in the first chapter, compiled by Prof. 

 Haga and others, a detailed description of the labor- 

 atory and of the more important machinery and 

 fittings, particularly those belonging to the " cryo- 

 genic " department, to which Prof. Onnes has devoted 

 most of his personal labours ; the low temperature 

 baths prepared here are extensively used throughout 

 the laboratory for various researches. 



In an appendix to this chapter Dr. Siertsema gives 

 an interesting account of the training school for 

 apprentice mechanics instituted by Prof. Onnes in 

 connection with the laboratory. This institution is 

 probably unique; it was started in 18S6 with one pupil, 

 and the number has risen steadily until this session 

 no less than thirty-three boys are receiving systematic 

 instruction in the various mechanical arts, with 

 the object of qualifying themselves as instrument 

 makers, glass-blowers, electricians, and for similar pro- 

 fessions. The boys are supposed to assist to a certain 

 extent in the routine work of the laboratory and earn 

 corresponding small wages, while in the evening they 

 have to attend classes in the municipal technical 

 institute. A better training for the purpose could 

 hardly be imagined, and one is not astonished to learn 

 that after the completion of the three years' course 

 the boys appear to be much in request in laboratories 

 and various engineering and technical works. 



In chapter ii. thermodynamical investigations are 

 reviewed ; Prof, van der Waals gives an account of 

 Prof. Onnes's researches on thermody'namical surfaces, 

 Prof. Kuenen writes on the phenomena of condensa- 

 tion of binary mixtures, and there are further articles 

 on accurate isothermals of gases, on the construction 

 of models of surfaces, and on capillarity and viscosity 

 of liquids up to the critical region. 



The third chapter, edited by Prof. Lorentz and 

 others, is devoted to optical and magneto-optical 

 work ; here we find a discussion of experiments on the 

 reflection of light by mirrors, on the magnetic rota- 

 tion of the plane of polarisation in gases, liquefied 

 gases and other liquids, on the influence of pressure 

 on the rotation of sugar solutions, on the reflection of 

 light by magnetised mirrors (Kerr's phenomenon), and 

 an account of Zeeman's discovery of the modification 

 in spectra by magnetic forces. The phenomenon dis- 

 covered by Egoroff and Georgiewsky, that a sodium 

 flame placed in a magnetic field emits partially 

 polarised light, was investigated by Prof. Lorentz 

 himself, and appears to be closely connected with 

 Zeeman's phenomenon. 



In the last chapter Prof. Zeeman gives a description 

 NO 1836, VOL. 71] 



of researches on Hall's phenomenon in bismuth at 

 various temperatures down to the boiling point of 

 oxygen, measurements of the dielectric constant of 

 liquid oxygen and liquid nitrous oxide, and of the 

 absorption of Hertz vibrations by salt solutions. 



A detailed account of all the research work is pub- 

 lished regularly in the Communications from the 

 physical laboratory at Leyden, the issue of which was 

 commenced in 1892, but the present papers give a 

 useful general summary of the work carried out, pre- 

 sented in a manner which should make it intelligible 

 to the uninitiated. 



The volume bears ample testimony to the success 

 which has attended Prof. Onnes's manifold labours for 

 his laboratory, which owes to him its position as one 

 of the best known institutions of its kind. It is well 

 illustrated, and contains as a frontispiece a striking 

 likeness of Prof. Onnes, apparently after a drawing. 



PRACTICAL SILICATE ANALYSIS. 

 Manual of the Chemical Analysis of Rocks. By H. S. 

 Washington, Ph.D. Pp. ix+183. (New York: 

 Wiley and Sons; London : Chapman and Hall, Ltd., 

 1904.) Price Ss. 6d. net. 



OF late years greatly increased attention has been 

 directed to the chemical investigation of rocks, 

 and the science of petrology has been enriched by many 

 excellent analyses. Among these the work of the 

 United States Geological Survey deservedly holds the 

 highest place, both on account of its abundance and 

 its thoroughness. The present treatise arises from an 

 endeavour to make the methods used by Clarke, 

 Hillebrand, and other chemists in the United States 

 laboratory available to all workers. It is excellently 

 clear and detailed, and though the experienced analyst 

 will not find in it much that is not already published 

 in more succinct form in the ofificial Bulletins of the 

 Survey, he will glean a few details of manipulation 

 and discussions of the bearings of chemical petrology 

 that will at any rate repay perusal. 



The author intends his book to be used mainlv by 

 the rather numerous class of geologists and petro- 

 logists who combine a fair knowledge of chemistry 

 with a desire to make their own rock analyses. L'n- 

 doubtedly this is a far more satisfactory proceeding 

 than, as is usually done, to have the analyses executed 

 by some analyst who has no special knowledge of the 

 intricacies of this part of practical chemistry, and 

 follows methods which are discredited or discarded. 

 In any case such a worker will do well to place him- 

 self, for a time at least, under some teacher who is 

 thoroughly at home in the subject ; we hope that this 

 book will not stimulate the production of analyses of 

 rocks by students in course of training. Much of the 

 worst analytical work with which chemical petrology 

 is burdened has been executed in that way. If it helps 

 to spread the knowledge of the methods used by Clarke 

 and Hillebrand this book will do much good, as it is 

 desirable that these should henceforward be recognised 

 as standards, from which any important departure 

 should be notified when the results are published. 



In a few respects Dr. Washington has simplified the 



