:go 



NA TURE 



[July 25. 1907 



late Mr. Danford and by Dr. Bowdk-r Sliarpe, who 

 read there an important paper on the classification of 

 birds. The presidents on this occasion were Prof. 

 Victor Fatio, of Geneva, and Dr. Otto Herman, of 

 Budapest. The ne.xt meeting- of the congress was 

 deferred for several years from various causes. But 

 the difficulties were at length surmounted, and the 

 ornithologists of every part of the world were invited 

 to assemble at Paris in June, 1900, under the pre- 

 sidency of the late Dr. Oustalet, the head of the 

 magnificent collection of birds in the Jardin des 

 Plantes. Although ornithologists are not numerous 

 in France, the meeting in Paris was very w'ell 

 attended, and included visitors from all parts of the 

 world. Many excellent communications were made 

 to it. .\t the close of the seances it was resolved that 

 the next (fourth) meeting of the congress should take 

 place in England in 1905, and Dr. R. Bowdler 

 Sharpe, the well-known head of the Bird Depart- 

 ment at the Natural History Museum, South Ken- 

 sington, was selected as its president. The present 

 volume gives us a full account of the proceedings of 

 this meeting, which was held in London in June, 

 1905, and was attended not only by the English de- 

 votees of ornithology, but by representatives of that 

 science from France, Germany, Austria, Hungary, 

 Italy, Holland, Belgium, Russia, Sweden, Switzer- 

 land, the United States, Canada, and Australia. 



The fourth congress was opened at the Imperial 

 Institute, South Kensington, on June 12 by a 

 few words from the outgoing president. Dr. 

 Oustalet, who then vacated the chair in favour 

 of Dr. Sharpe, the new president. Dr. .Sharpe 

 gave a most interesting and instructive address 

 on the origin and progress, from 1753 to the 

 present time, of the national bird-collection in the 

 British Museum, which is now by far the finest and 

 most nearly complete of its kind in the world. This 

 address, which is printed in full in the present 

 volume, gives particulars of the additions made to 

 the great collection year by year since its foundation, 

 together with details on its mode of arrangement and 

 government. By bequest, purchase, and presentation. 

 Dr. Sharpe tells us, nearly everv large private col- 

 lection of birds made in England has ultimately 

 passed into the British Museum, including those of 

 the late Marquess of Tweeddale, Mr. Seebohm, Mr. 

 Crowley, Mr. Allan Hume, Dr. Sclater, Mr. Osbert 

 Salvia, Dr. Godman, and other well-known natural- 

 ists. 



After the president's address the present volume is 

 mainly occupied with the papers read at the meetings 

 of the congress and at its various sections. These 

 sections were five in number — systematic orni- 

 thology and distribution ; migration ; biology and 

 nidification ; economic ornithology; and avicul- 

 ture. Excellent communications, altogether forty in 

 number, were made on all these subjects. They are 

 mostly of a somewhat technical character, but we 

 ■may direct attention to Mr. Walter Rothschild's paper 

 on extinct and vanishing birds, which was splendidly 

 Illustrated by the large series of specimens and draw- 

 ings shown to the ornithologists when they made 

 NO. 1969, VOL. 76] 



'ce 



if- 



4 



their excursion to Tring. We may also invite notice 

 to Mr. Pycraft, who writes on the origin of the dif- 

 ferences between the various kinds of nestlings, and 

 seeks to justify his ingenious theory that all birdi 

 " were originally arboreal." 



Those who require information on the eleven \c\ 

 for the Protection of Wild Birds passed by our Pap 

 liamcnt may refer to Sir Digby Pigott's paper on 

 this difficult subject read before the economic sec- 

 tion, while those who keep birds in aviaries should 

 not fail to study Mr. D. Seth Smith's address on the 

 importance of aviculture as an aid to the study of 

 ornithology. The numerous and interesting facts 

 ascertained by the votaries of this new branch of 

 science are well set out in Mr. Seth Smith's contri- 

 bution to the present volume. 



THERMODYKAMICS. 

 Therwodyiiainics : an Introductory Treatise dealing 

 mainly with First Principles and their Direct Ap- 

 plications. By Prof. G. H. Bryan, F.R.S. Pp. xiv + 

 204. (Leipzig : B. G. Teubner ; London : D. Nutt ; 

 Williams and Norgate, 1907.) 



PROF. BRYAN has not been content in 

 this work to follow closely the beaten track, but 

 has given us the results of much original research. 

 The fundamental conceptions of energy, available or 

 unavailable, of entropy, and of temperature are given 

 in their simplest form (see the general summary 

 at end of the book). 



As the conception of temperature is for the most 

 part new, and throws much light on the subject, it is 

 well to set out the author's definition. The absolute 

 temperature of a body M is to be understood, and 

 can be defined, onl)' with reference to another stan- 

 dard body N. It is the ratio between the quantities 

 of heat respectively taken from M and imparted to 

 N, when M is used as reservoir, N as refrigerator in 

 a reversible Carnot cycle. This, of course, is, and is 

 intended to be, a theoretical definition only; and a 

 theoretical definition is needed. Similarly, the 

 entropy of a body cannot be defined as an absolute 

 quantity. We can only say that in certain cir- 

 cumstances it increases or diminishes. In all irre- 

 versible transformations it increases by an amount 

 equal to the available energy transformed into un- 

 available energy. Two definitions of entropy are 

 given at p. 58. 



Prof. Bryan encounters the usual difficulty in de- 

 finina' temperature, density, &c., at a point in a 

 molecular medium. Given a continuous medium, we 

 say that (for instance) the density at P is the limiting 

 ratio of quantity to the containing volume when that 

 volume (which contains P) becomes infinitely small. 

 That definition is irreproachable, but, as applied to a 

 medium consisting of discreet molecules, wholly 

 devoid of meaning. It is possible to give a logical 

 definition by proceeding to the limit in the other 

 direction. But in practice — and Bryan follows the 

 practice — it is usual to define density as the number of 

 molecules in an element of volume at P — large com- 

 pared with molecular dimensions, it being assumed 

 for the purpose of the definition that the density may 



