268 



SCIENCE. 



[N. S. ^'0L. XV. No. 372. 



feature which adds interest and value to the 

 book, is the frequent allusion to general zoolog- 

 ical theories. For example, the relations of 

 the Nemertini to the theories of the origin of 

 metamerism are considered in sufficient de- 

 tail to make the matter clear. On this par- 

 ticular question the author takes no positive 

 stand one way or the other, but is inclined, on 

 the whole, to follow Hatschek and Mayer. 

 These additions greatly enhance the general 

 interest of technical works like the one under 

 consideration and materially lessen the burden 

 of the load of detail which the student must 

 struggle under. 



The style of writing, although somewhat 

 heavy, is clear and definite, and awkward 

 phrases like 'a pair of groups,' and 'than 

 which,' or careless statements, such as 'the 

 very close relationship of these two groups 

 (Turbellaria and Nudibranch molkises) with 

 the Coelenterata ' (p. 12), are rarely encoun- 

 tered. The author piits himself in the way 

 of a great temptation by describing at the out- 

 set what he considers to be an 'ideal' Platyhel- 

 minth, and throughout the book we find him, 

 consciously or unconsciously, setting up this 

 ideal as a phylogenetic fetish. Such a method 

 of presentation may or may not be subject to 

 criticism, according as the book is to be used 

 as a text-book or as a reference book. The 

 'type' method is very handy for teaching pur- 

 poses, but as a basis for phylogenetic deduc- 

 tions it appears somewhat out of place and 

 becomes a source of possible error. These are 

 but minor criticisms, however, and may be 

 easily overlooked when we consider the many 

 merits and interesting suggestions which the 

 author has embodied in this volume. 



Gary N. Calkins. 



Columbia Univeesity. 



Yale Bi-Oentennial Publications. Contribu- 

 tions to Mineralogy and Petrography from 

 the Laboratories of the Sheffield Scientific 

 School of Yale University : Edited by S. L. 

 Penfield and L. V. Pirsson. 1901. With 

 three plates and several figures. 

 The volunae comprises 'a series of reprints 

 from some of the most important of the papers 

 containing the results of the researches made 



in the chemical, mineralogical and petrograph- 

 ical laboratories at Yale in the lines of miner- 

 alogy and petrography.' Part I. by Professor 

 Penfield includes a history of the mineralogical 

 department and of the development of miner- 

 alogy at Yale, which goes back to the first 

 years of the last century and continues since 

 then to represent American mineralogical re- 

 search. A bibliography of mineralogical pa- 

 pers and summary of new mineral species 

 determined, or of formulas established, is add- 

 ed. Forty-three papers on mineralogical sub- 

 jects are reprinted, mainly from the American 

 Journal of Science between 1850 and 1901; the 

 authors are S. L. Penfield, Geo. J. Brush, E. 

 S. Dana, H. L. Wells and others. Part II. by 

 Professor Pirsson gives a similar history and 

 bibliography for the petrographical depart- 

 ment, which, notwithstanding its comparatively 

 recent organization, makes a valiant exhibit 

 even compared with its older companion. 

 Eight petrographic papers, several of classic 

 interest to American petrographers, are re- 

 printed. The volume is a valuable collection 

 of important papers, and a striking record of 

 original research in the departments included. 

 John E. Wolff. 

 Hakvakd University. 



Velocity Diagrams. By Chas. W. MacCord, 



A.M., ScD. New York, J. Wiley & Sons; 



London, Chapman & Hall. 1901. 8vo. Pp. 



113. Pigs. 83. $1.50. 



Professor MacCord has published in this 

 form an abstract of lectures forming a part of ' 

 his course of instruction, illustrating his meth- 

 ods of treatment of problems in kinematics 

 involving the construction of 'velocity dia- 

 grams' and supplementing the work embodied 

 in his larger treatise on 'Kinematics of Prac- 

 tical Mechanism.' He has, for many years, 

 found this class of graphical construction pe- 

 culiarly interesting as bearing upon the work 

 of the designing engineer planning combina- 

 tions of mechanical movements, and he has 

 developed this feature of his work with rare 

 skill, ingenuity and practicality. The occa- 

 sional appearance of an article by the same 

 hand in the technical journals, notably in the 

 Scientific American Supplement, has been al- 



