December 13, 1900] 



NATURE 



153 



the remarkable "mimicry" of the plane by the sycamore, 

 will serve to indicate the amount of attention bestowed 

 by the author on botanical subjects. The incident related 

 on page 87, narrating how a Scotch minister caused all 

 the daffodils in his churchyard to be mown down because 

 his wife regarded yellow as a vulgar colour, is a curious 

 example of mid-century "asstheticism." To those fond 

 of their gardens, the hints given as to the kinds of shrubs 

 and herbaceous plants that flourish best in this country 

 will be acceptable. 



With the number of subjects on which the author 

 touches it would not be surprising if he fell here and 

 there into error. And yet there are but two passages 

 which we have found occasion to criticise in this respect. 

 In the first of these (page 89) we fail to realise how ice is 

 likely to have had any share in the transport of the re-' 

 mains of the Bernissart iguanodons. The other is the 

 statement (p. 46) that the nightjar, or goatsucker, is a 

 relative of the swallow, whereas it is, of course, to the 

 swifts that this bird is really allied. That the statement 

 is not due to an accidental slip of the pen is proved by 

 its repetition on page 233. These, however, are but 

 trivial blemishes. And to whatever page he may turn, 

 the reader can scarcely fail to be interested in what the 

 author has to tell him. Whether, indeed, to while away an 

 idle half hour at home, on a railway journey, or as a 

 companion in the field, it would be difficult to find a 

 more entertaining and instructive work of its kind. The 

 epithet " delightful " suits it exactly. R. L. 



OUR BOOK SHELF. 



Cinematique et Mecanismes, Potentiel et Mecanique des 

 Fhddes. Cours Professe k la Sorbonne. Par H. 

 Poincare ; redigd par A. Guillet. Pp. i -f- 385. (Paris : 

 Carre et Naud, 1899.) 



This book is edited from a course of lectures given at 

 the Sorbonne. The first part deals with the kinematics 

 of rigid bodies in two and in three dimensions, including 

 the theories of roulettes, of acceleration centres and of 

 relative motion ; and concludes with a chapter on simple 

 mechanisms. These are all well-worn topics, and afford 

 little opportunity for novelty of treatment. In the {t.^ 

 pages devoted to finite rotations we notice, however, an 

 elegant method of investigating Rodrigues's formulae 

 which is, at all events, not current in this country. The 

 exposition is marked throughout by the author's usual 

 facility, and the illustrations are well chosen. A severe 

 taste might perhaps take exception to the way in which 

 analysis and geometry are continually mixed up in the 

 proofs, but a course of lectures intended primarily for a 

 special class of students is not to be judged by the same 

 cancms as a formal treatise. 



The second part gives, in about 180 pages of large 

 type, a rapid sketch of the theory of the potential, the 

 attraction of ellipsoids, hydrostatics and hydrodynamics. 

 A number of leading propositions are introduced, but the 

 treatment is necessarily fragmentary, and in some in- 

 stances it might be difficult to account for the precise 

 selection which has been made. The brief chapter on 

 hydrodynamics is disappointing. We notice, in particular, 

 that Poisson's proof of Lagrange's velocity-potential 

 theorem is reproduced without a word of warning as to its 

 defects ; and on p. 330 we have the following mysterious 

 sentence : " On a discute la question de savoir si un liquide 

 visqueux est encore soumis au theor&me de Lagrange ; 

 les opitiions sont partages ! " Again, on p. 339, the 

 remark : " II est impossible de determiner theorique- 



NO. 1624, VOL. 63] 



ment le coefficient de contraction," might surely be 

 qualified. It is a little strange to find the labours of 

 Stokes and Kirchhoff" on these points entirely ignored, 

 even in an informal publication like the present. The 

 absence throughout of all reference to authorities is, in- 

 deed, to be regretted ; such references can, of course, be 

 only sparingly made in actual lectures, but they might 

 well be introduced in the process of editing. 



It would be ungracious not to add that although, from 

 the nature of the subject, the present treatise is not likely 

 to excite such widespread interest as some of its prede- 

 cessors, probably few readers will be found to lay it down 

 without a fresh feeling of admiration for the energy and 

 versatility of its author. H. L. 



A Contents- Subject Index to General and Periodical 

 Literature. By A. Cotgreave. Pp. xii -}- 744. (Lon- 

 don : Elliot Stock, 1900.) 



This is an attempt to bring together and classify in 

 alphabetical order the noteworthy contents of periodicals 

 and some other publications. 



Several indexes to periodical literature are in existence, 

 and are appreciated by people who have cultivated the 

 habit of verifying references. Mr. Cotgreave has produced 

 an index which will prove a handy and inexpensive guide, 

 and an examination of it suggests that a similar work, 

 prepared by a body of experts instead of one man, and 

 issued periodically, would be of distinct value. 



The index is not complete — nor does it pretend to be, 

 but it is a praiseworthy attempt to classify a mass of 

 heterogeneous articles, books and papers into subjects. 

 Any one desirous to know a few contributions on any 

 subject has only to refer to the index and he will find 

 some to serve his purpose, though not always the best. 

 We are only concerned with the scientific subjects, and 

 have examined the entries from this point of view. The 

 result is not very satisfactory, for some of the best con- 

 tributions to science do not appear — at any rate where 

 we should naturally expect to find them. Why should 

 BarfFs "Chemistry" and Reynolds' "Chemistry" be 

 selected as containing accounts of the composition of air, 

 while many other much better descriptions have been 

 published ? Why, again, should Johnston's " Chemistry 

 of Common Life" be the only book given under the 

 composition of air? Under physical geography there 

 are six titles, three of which are unimportant ; the only 

 title under natural philosophy is Mitchell's " Orbs of 

 Heaven " ; an article on cellulose is classified under 

 natural science ; Balfour Stewart's Physics Primer is the 

 only book cited under the title " laws of electricity " ; 

 Ashby's " Physiology " is the only reference given for a 

 description of the metric system ; the British Museum 

 catalogue and introduction to the study of meteorites 

 is not mentioned under meteorites ; and many other 

 similar cases could be given. We understand, of course, 

 that the index is an eclectic one, and are willing to 

 acknowledge that much work must have been expended 

 in its preparation ; but its limitations and imperfections 

 must nevertheless be pointed out. If it is borne in mir»d 

 that the book only contains a general survey of literature, 

 it will be found of service. 



Workshop Mathematics. By Frank Castle, M.I.M.E. 

 Part i., pp. viii -f- 154. Part ii., pp. ix+ 177. (Lon- 

 don : Macmillan and Co., Ltd., 1900.) 



Prof. Perry's persistent advocacy of a system of mathe- 

 matical instruction adapted to modern requirements is 

 bearing fruit in the shape of text-books, which will 

 probably do more to induce teachers to adopt rational 

 methods than the most convincing statement in favour of 

 them. Mr. Castle has already prepared a book on 

 " Practical Mathematics " which covers substantially all 

 the subjects in the syllabus drawn up by Prof Perry for 



