562 Scien fific In telligm.ce. 



Supplementally reading is facilitated by the appendix which con- 

 tains ninety bibliographical references. Most of the illustrations 

 are new, all of the diagrammatic figures are clear cut and illumi- 

 nating, and the numerous half-tone reproductions of original 

 photographs are excellent. Xot only is the author's style 

 unusually pleasing and logical, but his wide experience in research 

 has enabled him to present the subject in a finished, masterly 

 manner. Unquestionably the book constitutes a valuable contri- 

 bution to the subject and it merits the attention not only of all 

 students and teachers of physics, but also of those musicians who 

 desire to acquire a full appreciation of the scientific foundation of 

 their special art. h. s. u. 



10. Theory of Errors and Least Squares ; by LeRoy D. 

 Weld. Pp. xii, 190. New York, 1916 (The Macrnillan Co.). — 

 In the preface the author says : " This small volume embodies 

 the material used by the writer as lecture notes during the past 

 twelve years. It is intended as a presentation of the Theory of 

 Errors and Least Squares in such a simple and concise form as to 

 be useful, not only as a text-book for undergraduates, but as a 

 handy reference which any research worker cau read through in 

 an evening or so and then put into immediate practice." 



In the very nature of the case, the ground covered does not 

 afford anything especially novel, but, on the other hand, the 

 manner of presentation seems to be unusually clear. This condi- 

 tion is largely brought about by the inclusion in the text of numer- 

 ous practical illustrations taken from the fields of astronomy, 

 chemistry, physics, surveying, etc. Scattered through the text 

 and at the ends of the chapters 126 problems for solution by the 

 reader may be found. The appendix contains supplementary 

 notes on mathematical proofs and a collection of important defi- 

 nitions, theorems, rules and formulas for convenient reference. 

 We heartily agree with the author's statement that "... for 

 some reason, students are rarely given opportunity to acquire 

 facility in these lines, the result being that too many of our sci- 

 entists and engineers go about their work without such equip- 

 ment," and hence we are glad to see that one possible cause for 

 this condition — the non-existence of a short, practical text— has 

 been completely removed by the present useful contribution. 



h. s. v. 



II. Geology axd Mineralogy. 



1. The Strophomenidce of the Krlstiania region • by Olaf 

 Holtedahl. Videnskaps. Skrifter, I. Mat.-Xaturv. Klasse, 

 1915, !No. 12, 1916, pp. 1-117, 16 pis., 7 text figs. — It is now more 

 than twenty years since Kail and Clarke published their most 

 excellent revision of Paleozoic Brachiopoda, and yet in all this 

 time but very few Europeans have thought it worth while to 

 revise their forms in the light of this far-reaching study. Buck- 

 man of England now has an associate in Holtedahl, and we hope 

 the example set by these Old World pioneers in the study of 



