August 20, 1908] 



NATURE 



365 



On the whole, the book should fulfil the wishes of 

 the author — to supply a long-felt want in the German 

 language in the shape of a short treatise on higher 

 geodesy — though, as explained by Dr. Buchholtz in 

 his admirable preface, many important and recent 

 acquisitions to our knowledge of this subject have not 

 been treated in the present volume, and remain to 

 appear, we may hope, in a further contribution from 

 the author. 



It remains to mention that the whole book is ex- 

 cellently supplied with diagrams for the help of the 

 student. W. J. J. 



ELEMENTARY SCIENCE. 

 (i) The Principles of Pliysics. By A. P. Gage. Re- 

 vised by A. W. Goodspeed. Pp. viii+547. (Boston 

 and London : Ginn and Co., n.d.) Price 6x. 6d. 



(2) Die Eleklrizitat ah Liclit und KraltqucUc. By 

 Dr. P. Eversheim. Pp. viii+121. (Leipzig: Quelle 

 and Meyer, 1907.) Price 1.25 marks. 



(3) Elementary Science for the Certificate Examin- 

 ations. Edited by W. Briggs. Introductory Sec- 

 tion. Pp. iv-l-256. Price 2S. 6d. Section A, Chem- 

 istry. Pp. vii+192. By H. W. Bausor. Price 2s. 

 Section B, Physics. By John Satterly. Pp. viii + 

 352. Price 3^. (Cambridge : LTniversity Tutorial 

 Press, 1908.) 



( I ) ' I 'HIS is a revised edition of a book which 

 -L appeared in 1S95, and the plan has been con- 

 siderably altered in order to bring it into line with 

 modern requirements. Sections have been omitted 

 which in the opinion of the reviser are of little use 

 to elementary students. These omissions consist 

 chiefly of experiments to be performed by the student 

 and the more remote applications of principles. New 

 sections have been added describing in an elementary 

 way the results of recent researches and practical 

 applications. The plan adopted throughout the book 

 has been to avoid so far as possible proofs of mathe- 

 matical formula;, and to explain the principles by 

 experimental and descriptive methods. The first 150 

 pages are devoted to the subject of experimental 

 mechanics. Sound, heat, light, including the elemen- 

 tary parts of interference, diffraction and polarisation, 

 and electricity and magnetism form the rest of the 

 volume. The statement on p. 229 is evidently an 

 error, viz. : — 



" Since liquids must be contained in a vessel of 

 some sort the observed expansion is usually not that 

 of the liquid alone, but a value greater than the real 

 expansion of the liquid by the increase of volume of 

 the vessel." 



Again, on the same page india-rubber is cited as 

 having a negative coefficient of expansion. An 

 example of this kind should certainly be avoided with 

 elementary students, the apparent contraction when 

 heated being due to change in the elastic constant. 

 The statement in italics on p. 278 is likely to confuse 

 an elementary student, viz. " The illuminating power 

 of light diminishes as the square of the distance from 

 the light source increases." " Intensity of illumin- 

 ation " is better, "illuminating power" being re- 

 garded as a constant for the source of light. 

 NO. 2025, VOL. 78] 



The book is very well printed, and the illustrations 

 are clear. It may be safely recommended to students 

 who take up physics as part of their general educa- 

 tion. 



(2) " Elelvlrizitat," by P. Eversheim, is a small book 

 describing some of the present-day applications of 

 electricity. It is intended for the general reader, or 

 for those who have only a very slight acquaintance 

 with the elementary facts of electricity. 



The author first describes the various methods by 

 which a current of electricity may be produced, and 

 then proceeds to explain the phenomena of electro- 

 magnetic induction and the principles of the dynamo 

 and motor. Practical applications are then dealt with, 

 the subjects treated including electric lighting and 

 various types of lamps, transmission of power, the 

 electric telegraph, cable telegraphy, the telephone, 

 electric waves, and wireless telegraphy. 



.As a rule, the explanations of phenomena are clear 

 and accurate, and should be intelligible to the general 

 reader, but the diagram on p. 9 will not give him a 

 correct idea of the magnitude of thermoelectric cur- 

 rents, viz. a single couple with junctions at 0° and 50° 

 joined to an ammeter reading one ampere. Again, in 

 a book of this size one cannot expect full historical 

 treatment, but the omission of the name of Faraday 

 from the chapter on electromagnetic induction cannot 

 be passed over without comment, especially when 

 that of Lenz is included. 



In Fig. 56, p. 113, " Braun " system of wireless 

 telegraphy, the " earth connection " is in the wrong 

 place. The " Aerial " should be earthed. In Fig. 58 

 the " earth connection " or " balancing capacity " are 

 omitted. At the end of the book is a short section 

 referring the reader to larger treatises on the subject 

 of electricity and its applications. 



(3) These three manuals comprise a course in 

 elementary science suitable for the certificate and pre- 

 liminan,' certificate examinations for 1909. The intro- 

 ductory section deals with the elementary measure- 

 ment of length, area, volume, mass, density, &c. ; 

 properties of matter ; thermometry and expansion ; 

 nature and composition of air and water ; action of 

 acids on metals, and of heat on some organic sub- 

 stances. The fundamental facts are well illustrated 

 throughout by simple experiments to be performed by 

 the student. 



Section A is a further continued course in chemistry. 

 The properties and interactions of some common sub- 

 stances are dealt with experimentally, and the funda- 

 mental laws of chemistry explained. The author has 

 avoided formula and equations of reactions so far as 

 possible in the text, introducing them in an appendix 

 at the end. 



Section B is a continuation of the physics course ; 

 mechanics, heat, light, electricity and magnetism are 

 dealt vi'ith, the facts being well illustrated by simple 

 laboratory experiments. The explanation of multiple 

 reflections from thick mirrors avoids a very common 

 error usual to text-books, but it is not true to say that 

 all the images are on the normal to the mirror 

 through the object. Fig. 33, p. 337, is misleading if 

 intended to illustrate the probable result of the ex- 

 periment numbered 37. 



