180 



KNOWLEDGE. 



[AuousT 1, 1896. 



It is not arranged in a way to be of any use as a book of 

 reference, and is scarcely popular enough to be of general 

 interest. We must therefore take it as a book merely of 

 passing interest to bird lovers, and as this it makes very 

 pleasant reading, and brings back to our minds many a 

 day spent with the birds and the sea. 



James Clrrh- Maxitrtl iiml Moilern P/ii/.s/cv. By K. T. 

 Glazebrook, F.R.S. (Cassell.) " Century Science Scries." 

 Ss. fid. Mr. Gla/ebrook, in his preface to this short 

 memoir of Clerk Maxwell and his work, expresses the fear 

 that his attempt to explain to non-mathematical readers 

 the problems attacked by the great investigator, " without 

 the aid of symbols is almost foredoomed to failure." In 

 this we cannot agree ; for it is by no means impossible, 

 while avoiding the exact reasoning expressible only by 

 mathematical symbols, to 

 describe in words at least the 

 nature of the problems at- 

 tacked, and the conclusions 

 to which they lead. Unfortu- 

 nately, this attempt has some- 

 what overtaxed Mr. Cllaze- 

 brook's skill. The earlier part 

 of the book, dealing with the 

 life of Clerk Maxwell, is 

 brightly written and intensely 

 interesting. The anxiety of 

 the child to know the " par- 

 ticular go " of everything 

 around him made his 

 manner somewhat eccentric, 

 and gained for him among 

 his schoolfellows the nick- 

 name "Dafty." This eccen- 

 tricity developed later into a 

 genius for mathematics, in 

 which study Clerk Maxwell 

 easily eclipsed all his school- 

 fellows. And in 1846, when 

 he was barely fifteen years of 

 age, his genius was displayed 

 in a communication to the 

 Royal Society of Edinburgh, 

 " On the Description of Oval 

 Curves, and those having a 

 Plurality of Foci." It is in- 

 teresting to observe that 

 mathematical ability, like 

 musical genius, is almost 

 always of early development. 

 It was thus with Lord Kelvin, whose jubilee has just 

 been celebrated. 



An unfortunate misprint occurs over and over again in 

 Mr. Glazebrook's book, wherever the ratio of the specific 

 heats of gases is touched on. It is when the number 1-33 

 is given as the theoretical ratio between the specific heat 

 of an ideal gas at constant volume and at constant pressure, 

 instead of the correct number, 1-66. And this misprint 

 has the result of rendering obscure the whole explanation 

 of Clerk Maxwell's reasoning. It is especially to be 

 regretted that confusion is thus introduced into a 

 subject which it is most difficult to expound in popular 

 language. 



Clerk Maxwell must have been an ideal teacher for those 

 who possessed the will and the power to learn. The secret 

 of the success in teaching at Cambridge is contained in a 

 sentence of his introductory lecture : " The student who 

 uses home-made apparatus, which is always going wrong, 

 often learns more than one who has the use of carefully 



_/. ^2h/C rlu«ui^lL 



adjusted instruments, to which he is apt to trust, and 

 which ho dares not take to pieces." 



The biographical part of Mr. Glazebrook's book ends 

 with chapter vi., and chapters vii. to x. are devoted to 

 an exposition of Maxwell's researches. The account of 

 his experiments on vision is clear and essentially accurate ; 

 but it is unfortunately otherwise with his account of 

 Maxwell's share in the development of the kinetic theory 

 of gases. For example, while the conclusion is correctly 

 drawn that the specific heats of all gases are inversely 

 proportional to their densities, Mr. Glazebrook adds : 

 " This is the law discovered experimentally by Dulong and 

 Petit to be approximately true of a large number of sub- 

 stances." To anyone who knows the subject, Mr. Glaze- 

 brook's meaning, though obscurely expressed, is clear 



enough. lie would say that 

 the specific heats of elements 

 are inversely proportional to 

 their atomic weights, and 

 that these may be taken 

 (though with many excep- 

 tions) as proportional to the 

 densities of the elements in 

 the gaseous state. But, as it 

 stands, a much fuller explana- 

 tion is required to make the 

 passage intelligible. The 

 account of Prof. Bolzmann's 

 theorem of degrees of freedom , 

 on page 139, is quite un- 

 intelligible ; nevertheless it is 

 not impossible to express its 

 main features in popular 

 language. 



It is very difficult, too, to 

 derive any clear idea of Clerk 

 Maxwell's theories of elec- 

 tricity and magnetism from 

 Mr. Glazebrook's words ; and 

 yet the main features might 

 have been expressed so as to 

 be understood partially by 

 the half-scientific public. 



It is with regret that we 

 write in this deprecatory vein, 

 for the task which Mr. Glaze- 

 brook has set himself is a 



Fi'om James Chrk Ma.virell idkI Mudeni P//i/sics. 



praiseworthy one, and it is 

 a pity that his book cannot 

 be unreservedly praised. 

 Artistic anil Scientific Taxiclcrmi/ ami j\lodcllin(i. By 

 Montagu Browne, F.G.S., F.Z.S. (A. & C. Black,) 

 Illustrated. 21s. Some years ago Mr. P.rowne brought 

 out a very useful book on the subject dealt with in the 

 present volume, which is, however, much more advanced 

 and elaborate. With this book in his possession the 

 collector should be able to preserve and mount, either 

 artistically or scientifically, any specimen which he may 

 possess or obtain. Mr. Browne treats, in the most clear 

 and practical way, of the ways of collecting, skinning, 

 preserving, modellin.f;, casting, mounting, and grouping of 

 mammals, birds, insects, fish, and reptiles, and of the tools 

 and preservatives most useful for these purposes, besides 

 the methods of modelUng and casting of rocks, trees, and 

 flowers. When we add that the author has had long 

 personal experience as curator of a large museum, we are 

 sure that no further commendation on our part is needed. 

 That this is the best and most useful book on the subject 

 ever published is undeniable. 



