Chemistry and Physics. 327 



13. A B C of Hydrodynamics ; by R. de Villamil. Pp. 

 xi, 135, with 48 figures. London, 1912 (E. & F. N. Spon). — Con- 

 cerning this book the author frankly says : " There is not very 

 much that is new in it ; some of the quotations are so old that 

 they have been forgotten, and so will appear to the reader of the 

 ordinary text-books as if they were new. What is, I fancy, orig- 

 inal is the way in which the matter is arranged and the subject 

 presented ". These statements are so modest as to be almost mis- 

 leading, for the topics discussed are treated in such a clear, 

 refreshing and common-sense manner as to give to the whole a 

 high percentage of effective novelty. In other words, the text is 

 very suggestive and it contains much wholesome food for thought, 

 not only for students who are commencing the study of hydrody- 

 namics but also for those who are thoroughly acquainted with 

 the advanced mathematical treatises on the subject. 



The text abounds in pertinent quotations from the writings of 

 recognized authorities. At the end of each chapter a summary 

 of the conclusions reached therein is given and. a short list of 

 " References " is appended. Although a few formulae are quoted, 

 the book can be profitably read with almost no knowledge of 

 mathematics. A number of admirable experiments are suggested 

 in the text and made clear by the associated diagrams. The 

 index is preceded by a short appendix which touches upon the 

 closely related subject of aerodynamics. h. s. u. 



14. Geometrical Optics; by Archibald Stanley Perctval. 

 Pp. vii, 132, with 59 figures. London, 1913 (Longmans, Green 

 and Co.). — The author's object in publishing this volume is stated 

 as follows : " This book is primarily intended for medical students 

 as a text-book on the subject of Geometrical Optics for their pre- 

 liminary scientific examinations, though it practically contains 

 all the Optics required by an ophthalmic surgeon. It is hoped 

 that it will also prove of service to students of physics, ..." A 

 fair idea of the scope of the text may be obtained from the titles 

 of the chapters, which are : " I Illumination — Pinholes — Shadows, 

 II Reflection at Plane Surfaces, III Reflection at a Spherical 

 Surface, IV Refraction at Plane Surfaces, V Refraction at a 

 Spherical Surface," and " VI Lenses." The explanations are very 

 clear and as simple as possible. The proofs of the formulas are 

 sufficiently rigorous, and special emphasis is laid on the consistent 

 and general use of algebraic signs. A few " questions " are asked 

 at the end of each chapter and the answers are given just before 

 the index. Also, a number of illustrative " examples " are formally 

 stated, and the solutions worked out, in the text. The appendix 

 treats of certain problems which are more difficult or intricate 

 than the ones given in the preceding chapters. A useful feature 

 of the book consists in the collection of formulas which follows 

 the appendix. 



Having thus far called attention only to the merits of the vol- 

 ume in question, it now seems fair to point out two significant 

 slips which the author has made. In the fine print, on page 42, 



