Feb. 19, 1880] 



NATURE 



367 



gasys seem not to have developed Ritualistic tendencies ; 

 but they have advanced notions concerning ornament, 

 bright colours look especially well on a brown skin, and 

 possibly before long a Malagasy bishop may appear in 

 full Ritualistic fig, evolved out of his inner consciousness. 

 If so, may we be there to see. 



We have only been able to touch here and there on the 

 many interesting subjects discussed by Mr. Sibree. This 

 book is a most valuable addition to knowledge and very 

 entertaining. It contains several full-page illustrations 

 (not all new) and two maps. 



CLAUSIUS'S -'MECHANICAL THEORY OF 

 HEAT" 



The Mechanical Theory of Heat. By R. Clausius. 

 Translated by W. R. Browne, M.A. (London : Mac- 

 millan and Co.) 



THIS translation satisfies a real want of a tolerably 

 large class of students of science. It furnishes in 

 a volume of reasonable size a clear and readable account 

 of a subject, an acquaintance with which has until lately 

 been only obtainable by an English reader at the cost of 

 a great deal of research through the transactions and 

 memoirs of various societies. The name of its author 

 furnishes a sufficient guarantee of the accuracy of the 

 substance matter of the book, treating as it does of a 

 subject specially his own. The method of treatment 

 leaves hardly anything to be desired, even from the 

 point of view of a student previously ignorant of the 

 subject. The reader is nowhere perplexed by uncouth 

 symbols or analytical operations beyond those which 

 are familiar to all acquainted with the principles of the 

 differential and integral calculus. At the same time, 

 and perhaps partly in consequence of this avoidance 

 of complicated analysis, the reader is never allowed to 

 lose sight of the essential meaning of the symbols em- 

 ployed. Some of the chapters in the book will furnish a 

 valuable exercise in the meaning and value of partial 

 differential coefficients, even to a student who is not 

 specially interested in the physical questions discussed. 

 The same remark applies to some of the explanations 

 given in the mathematical introduction, on the nature of 

 the integral of a total differential in the case when the 

 condition of being an exact differential is not fulfilled, 

 explanations originally inserted, as the author tells us, in 

 consequence of objections made to his theory by Prof. 

 Decher. 



Any one wishing to gain a general acquaintance, 

 thorough as far as it goes, with the subject, can scarcely 

 do so with the expenditure of less time and labour than 

 are required for the perusal of this book. As a mathe- 

 matical study the book may replace some of the luxuriant 

 growths of modern geometry and analysis with great 

 advantage to the brains of the student. 



The translation is admirably done. It is hardly pos- 

 sible in reading it to recognise any traces of foreign 

 idiom. Occasionally we find some little confusion of 

 phraseology, probably arising from loose translation ; as 

 on page 210, where a rather curious description is given 

 of the ordinary process of changing the independent 

 variables from x,y, to $, >/> and this process is apparently 



referred to, a little lower down, as an "artifice." It is a 

 pity, too, and a little surprising, considering the array of 

 scientific talent mentioned in the preface as having been 

 applied to the correction of first proofs, that the book 

 should be disfigured by so many misprints. Not to speak 

 of great uncertainty as to the insertion or omission of a 

 comma between the two variables inside a bracket after a 

 functional symbol, and the sign X between two factors of a 

 product, there are many serious errors. Thus, for instance, 

 on page 69 we have "volumes" for "values:" on pages 1 17 

 and 1 24 we have the sign + f or X ; on page 1 87 we have d T 



for T. In equations (19) and (20) of page 190 we have — jp 



dT 



■■ dQ 



written instead of ,~, and the error is repeated twice 



lower down on the same page. The figure of the steam- 

 engine on page 237, described as an "imaginary one,'' 

 certainly strikes one as decidedly imaginary. The inser- 

 tion of a few valves in the figure at suitable places would 

 render it more satisfactory, at any rate to an unimagina- 

 tive reader. It may be hoped that these blemishes will 

 be removed when a second edition is reached of what, in 

 spite of them, is an exceedingly valuable addition to our 

 English mathematical literature. W. S. A. 



OUR BOOK SHELF 



Noxious and Beneficial Insects of the Stale of Illinois. 

 Third Annual Report. By Cyrus Thomas, State Ento- 

 mologist. Pp. 1-212. Svo. (Springfield, 1879 ) 



If we might be permitted to propose another title for this 

 book, we would suggest that of "An Essay towards a 

 Monograph of North American Aphides" But we fancy 

 such a title would be too much opposed to that borne on 

 the cover. We fear the Report is too profound to be of 

 service to agriculturists and horticulturists, otherwise 

 than on the same grounds that an intelligent mother of 

 a family is enabled, from the study of a medical dictionary 

 (intended for the use of the profesion only), to diagnose 

 the symptoms of measles, croup, and other ills that 

 infantine humanity is heir to. We might make the same 

 objection to the titles of a multitude of American scien- 

 tific publications. The axiom that " the end justifies the 

 means" scarcely needs being called into requisition in a 

 notice of this Report ; yet some uncertainty exists in our 

 mind as to the end aimed at. Does it consist in enabling 

 unscientific, but intelligent, farmers and horticulturists 

 to identify their plant-lice foes ? or is it intended as a 

 prominent contribution towards a knowledge of these 

 insects, to be made use of by scientific workers princi- 

 pally ? We do not attempt to solve the problem, but 

 prefer to regard the Report more especially in the last- 

 named light. 



Looking, then, at the scientific side of the question, we 

 see here a most valuable contribution to a natural history 

 of American Aphides, and in some respects we think it 

 would have been better had the author not been ham- 

 pered with the necessity of producing a popular report at 

 the same time. It is impossible to give an analysis of the 

 author's views on the many vexed questions in the life- 

 cycles of these noxious atoms. Much of the introductory 

 remarks on habits has been of necessity (and advisedly) 

 compiled, and the suggestions as to dimorphism (p. 31) 

 have, we think, been somewhat fully anticipated; still 

 there remain some very potent suggestions made by Dr. 

 Thomas ; not the least of which is in what form those 

 species that appear habitually to attack annual plants 

 only, pass the winter months ? 



