July 19, 1906] 



NATURE 



267 



only different developments of the same fundamental 

 ideas. 



In recent years. Prof. Levi Civita has published a 

 number of papers in the Mil dei l.incei dealing with 

 particular solutions ofthe equations of dynamics, and 

 in especial with stationary motions. At the invitation 

 of Prof. Dickstein he has now prepared a simplified 

 account of these researches for the transactions of the 

 " Prac matematyczno fizyczynych," published at 

 Warsaw. The orifrina' startinff point of the investi- 

 gation was the method of ignoration of coordinates, 

 but the conclusions have now been shown to be results 

 of a general principle applicable to any system of 

 ordinary differential equations. They form a develop- 

 ment of the work of Routh, and the stationary 

 motions investigated by the author of " Rigid Dy- 

 namics " are shown to belong to a particular class to 

 which Prof. Levi ("ivit.i gives the name of " mouve- 

 ments i\ la Routh." G. H. B. 



.4 TREATISE ON CHEMISTRY. 

 A Treatise on Cliemistry. By Sir H. E. Roscoe, 

 F.R.S., and C. Schorlemmer, F.R.S. Vol. i. The 

 .Non-Metallic Elements. New edition, completely 

 revised by Sir H. E. Roscoe. Pp. xii-l-931. (Lon- 

 don : Macmillan and Co., Ltd., 1905.) Price 21s. 

 net. 



SIR HENRY ROSCOE is to be heartily congratu- 

 lated by all chemists on the appearance of a 

 new edition of the first volume of Roscoe and Schor- 

 lemmer's "Treatise on Chemistry." This volume 

 deals chiefly with the non-metallic elemrnts, and is 

 now in its third edition. 



Many chemists remember the interest which the 

 first appearance of this volume excited in 1877. Printed 

 in large, clear type, with excellent illustrations, it was 

 recognised both here and on the Continent as a clear 

 and readable account of the facts relating to the 

 chemistry of the non-metallic elements. If the student 

 faik'd to find in it any new light on the obscurities of 

 chemical theory, he at any rate was put in posses- 

 sion, not merely of the facts, but of the facts stated 

 with a due regard for the history of their discovery 

 which was then and is still foreign to the ordinarv 

 "handbook." There were, moreover, many experi- 

 mental details of service to workers in the laboratorv 

 recorded in the volume which were at that time not 

 easily accessible to the ordinary student. During the 

 nearly thirty years which have elapsed since the first 

 edition appeared, many treatises have been published 

 ill other languages, notably in German, but the trea- 

 ti-- ■ of Roscoe and .Schorlemmer still retains a certain 

 individuality for which it will be valued. 



In preparing this edition Sir Henry Roscoe has had 

 the valuable assistance of several collaborators with 

 special knowledge, and their handiwork is to some 

 extent evident in the different literary treatment which 

 may be discerned in various sections of the book. 



The first section of the volume relates to the general 



principles of the science, including a description of the 



properties of gases and liquids, and a very intelligible 



account of the development of the atomic theory. .A 



NO 1 916. VOL. 74] 



clear sketch is given of the theory of electrolytic disso- 

 ciation. This portion of the volume would have 

 been improved bv some concrete illustrations of the 

 methods of determining atomic weights. .As it is, the 

 reader must be very much at sea in understanding 

 what this constant actually means, apart from the im- 

 plications of the atomic theory. 



The remainder of the book is occupied with an 

 account of the properties and modes of preparation of 

 each of the non-metallic elements and their chief com- 

 pounds. The history of each element is succinctly 

 and well described, and important industrial applica- 

 tions are also alluded to. There is an excellent account 

 of the modern manufacture of illuminating gas and 

 of acelvlene, as well as of the commercial processes 

 adopted for the production of a number of the elements 

 and their compounds which find industrial uses. 



There is also a very complete account of the prepara- 

 tion and properties of the new gases of the atmosphere, 

 argon, &c., which, while interesting, does not throw 

 any new light on the obscure chemical relationships of 

 these elements. In this connection the ab-ence of an 

 account of the periodic classification under the general 

 principles of the science is specially felt. It would 

 have been better to have included in the first part of 

 this volume a complete consideration of the general 

 principles of chemistry, including the determination of 

 atomic weights, instead of reserving the discussion of 

 the periodic classification and other matters of prin- 

 ciple for the subsequent volume relating to the metals. 

 When the first edition of this volume appeared, many 

 of the lecture experiments described were new. and 

 were of interest and value to the teacher. .\ number 

 of these are now generally familiar, whilst some of 

 those still described have since been improved upon. 

 This feature is indeed no longer a striking one in the 

 book. Very few- new lecture or laboratory experiments 

 are included. The teaching of chemistry is, however, 

 no longer conducted on the old lines, and perhaps the 

 teacher would not now look to a treatise of this kind 

 for this information. The fact that in some sections 

 of the work pains are taken to describe fully striking 

 lecture experiments whilst in other and newer sec- 

 tions this aspect is entirely neglected is a defect in the 

 general plan of the book which might be remedied in 

 future editions. 



This raises the question as to the characters which 

 such a work as this should possess to be of real utility 

 at the present day. Handbooks and text-books of 

 chemistry for the teacher abound, many of them ex- 

 cellent as practical guides to the work of the lecture 

 room and laboratory. Then there are more ambitious 

 works purporting to be of the nature of treatises. 

 These, however, are too often ill-assorted and ill- 

 considered collections of the facts and theories of 

 chemistry utterlv lacking in those literary qualities 

 without which no work of the kind can expect to ap- 

 peal to the general reader or to take any permanent 

 place in the literature of the science. There is still 

 room for a treatise in the broad sense of the word, in 

 which the facts and doctrines of modern chemistry are 

 expounded in a lucid manner free from the details and 

 technicalities which are essential in a handbook or 



