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THE POPULAR SCIENCE MONTHLY. 



follow, and the causes leading to their foun- 

 dation clearer." The first of the three di- 

 visons of the treatise deals with the charac- 

 teristics of the chemical atoms. The author 

 begins by stating briefly the necessity 

 for holding the atomic theory, and for a 

 knowledge of the atomic weights, and pro- 

 ceeds to discuss the determination of these 

 weights from vapor-densities, from the spe- 

 cific heat of solids, and by means of isomor- 

 phism. He then takes up the relations be- 

 tween the properties of elements and their 

 atomic weights, which have led to the group- 

 ing known as Mendelejeff's classification. 

 The second part of the work is devoted to 

 the statistics of the atoms, and in this di- 

 vision are discussed forms of combination of 

 the atoms, the law of atomic linking, and 

 valency. In the third division is treated the 

 dynamics of the atoms, or the doctrine of 

 chemical change. Separate chapters of this 

 section are devoted to chemical change pro- 

 duced by mechanical disturbance and by 

 the action of light, to heat and electricity as 

 causes and as effects of chemical change, to 

 the influence of mass in chemical action, and 

 to the stability of chemical compounds. The 

 author considers that the influence of mass 

 has been too little regarded by chemists, but 

 that its importance is being more and more 

 recognized. He expects great progress soon 

 to be made in the direction of chemical me- 

 chanics, pointed out by Berthollet at the be- 

 ginning of this century. Throughout the 

 volume he shows much solicitude that theo- 

 ries shall be recognized as valuable aids to 

 chemical research, but shall not be formed 

 too hastily, nor trusted too implicitly. 



Forms of Animal Life. By Georgk Rolles- 

 TON, D. M., F. R. S. Second edition, re- 

 vised and enlarged by W. Hatchett 

 Jackson, M. A. New York : Macmillan 

 & Co. Pp. 32 + 937. Price, $9. 



This comprehensive treatise is described 

 on the title page as a manual of comparative 

 anatomy, with descriptions of selected types ; 

 and the distinctive character of the book, as 

 the late Prof. Rolleston wrote in his preface 

 to the first edition, seventeen years ago, 

 "consists in its attempting so to combine 

 the concrete facts of zootomy with the out- 

 lines of systematic classification as to enable 

 the student to put them for himself into 

 their natural relations of foundation and su- 



perstructure." The present edition of the 

 work was begun by the author in 1879, the 

 rewriting of several portions being Intrusted 

 to Prof. Jackson, whom Prof. Rolleston fur- 

 ther requested to complete the revision in 

 case he was prevented from doing it himself, 

 and this his death made necessary. The 

 book consists of three sections, the first con- 

 sisting of descriptions of prepared types, 

 which include the rat and rabbit as types of 

 mammals, the pigeon, ringed snake, frog, 

 perch, and a representative of each of four- 

 teen other classes. The second section com- 

 prises descriptions of fourteen plates, four 

 of which are taken from the specimens de- 

 scribed in the first part of the work, five 

 others are from specimens of the same ani- 

 mals as described in the first part, but pre- 

 pared differently, and there are five plates 

 which relate to animals or groups not de- 

 scribed before. The remaining two thirds 

 of the volume is devoted to a general ac- 

 count of the animal kingdom, which has a 

 brief classification appended to each class or 

 group, and a bibliography of the most im- 

 portant and recent authorities, which will in 

 most cases give the names of all other ac- 

 counts worth reading. The two latter feat- 

 ures are additions which Prof. Rolleston de- 

 sired to be made in this edition, and the 

 third chief item of his plan was to enlarge 

 the descriptions of the preparations and ac- 

 counts of the various classes of animals, and 

 bring them up to the standard of contem- 

 porary knowledge. All this has been car- 

 ried out by Prof. Jackson, though the great 

 length of time which has elapsed since the 

 publication of the first edition has brought 

 with it so many and such vast changes in 

 comparative anatomy that great labor and 

 consequent delay became inevitable. 



A Critical History of Sunday Leoislation 

 FROM 321 to 1888 A. D. ByA. n. Lewis, 

 D. D. New York : D. Appleton & Co. 

 Pp. 279. Price, $1.25. 



Dr. Lewis has had occasion to make 

 extensive studies of the Sunday question 

 and its history, and particularly of the sub- 

 stitution in the Christian Church of the first 

 day for the original Sabbath of the seventh 

 day. The fruits of these studies are partly 

 embodied in polemical works which he baa 

 written in maintenance of the doctrines and 

 practice of the seventh-day Christians ; but 



