SCIENCE- GOSSIP. 



175 



Deschanel's Natural Pliilosophij, Pai't III. 

 Electricity. By J. D. Everett, M.A., D.C.L., 

 F.R.S. 358 pp., llf in. x 7^ in. (London : Blackie 

 & Son. 1901.) 4s. Gd. 



Treatises on electricity may be divided into 

 three classes ; namely, mathematical, experimental, 

 and descriptive. Those of the first two classes ap- 

 peal to the science student alone. The j)resent 

 treatise belongs to the third class, and as such is 

 accessible to the general reader. It contains a 

 fairly complete summary of the leading experi- 

 mental facts concerning electricity and magnet- 

 ism, together with descriptions and illustrations 

 of the principal apparatus used both in the 

 laboratory and in practical applications. It need 

 hardly be said that, in order to be kejat up to date, 

 a treatise on electricity must be in the main 

 newly written, and an examination of the book 

 before us shows that this has been done. A new 

 chapter contains an account of Maxwell's notions 

 with regard to electric action in dielectrics, but we 

 think it is a pity some reference to this is not 

 made in Chapter I. in connection with the old- 

 fashioned " one fluid and two fluid theories." Then, 

 again, magnetic hysteresis is fully discussed, and 

 the various meters — wattmeter, voltmeter, poten- 

 tiometer, ammeter, joulemeter, etc. — are included 

 among the apparatus described. In electro- 

 chemistry the modern theory of ionisation is 

 expounded ; while, among other new features, the 

 projDerties of electric oscillations are treated in a 

 chapter near the end. We have mentioned the 

 book as being descriptive rather than mathe- 

 matical, but nowadays no one can learn electricity 

 properly without knowing much of mathematics, 

 and Professor Everett has done wisely in intro- 

 ducing mathematical formulae where they are 

 required. To understand these, the reader must 

 be able to use the differential calculus ; and he 

 will also have to learn the meaning of such 

 phrases as ■' line integral," " surface integral," 

 " curl of a vector," especially in connection with 

 electric waves. To those who understand such 

 notations the formulae will give no difficulty ; those 

 who do not. will have to confine their attention to 

 the portions of the book dealing with general 

 descriptions, but it will not be long before they will 

 try to pick up the smattering of mathematical know- 

 ledge required to understand the rest. — (i. II. 11. 



Advanced Exercises in Practical P/ii/dcs. By 

 Arthur Schuster, Ph.D., F.R.S., and Chahles 

 H. Lees, D.Sc. 3li8 pp., llf in. x 7 in. (Cam- 

 bridge University Press. 1901.) 8s. 



We note that this volume is intended for 

 students who, having obtained an elementary 

 knowledge of experimental physics, desire to be- 

 come acquainted with the principles and methods 

 of accurate measurement. The large and increasing 

 number of students who have to be taught simul- 

 taneously in physical laboratories renders it neces- 



sary that the ijistructions supplied to them should 

 be fairly complete, and that the exercises should 

 be of such a nature as to eirable the teachers easily 

 to check the accuracy of the results obtained. A 

 demand has thus arisen for a text-book whicli will 

 supply students with most of the explanatory 

 matter required to enable them to work out the 

 experiments largely by themselves, and certainly 

 the present book gives the imjiression of having 

 been very carefully compiled for the purpose. As 

 no two physical laboratories are likely to be sup- 

 plied with exactly the same apparatus, a few short 

 hints contained in an appendix, giving the most 

 convenient dimensions of rods, tubes, etc.. have 

 been added. The ijrelirainary portion, dealing with 

 errors of obser\ation and such matters, willlje very 

 useful for the advanced class of students. The 

 exercises comprise mechanics, heat, sound, light, 

 magnetism, and electricity. — G. II. B. 



Shell Life: an Introduction to the Briiish Mol- 

 liisca. By Edw.\ru Step, F.L.S. 7j in. x 5 in., 

 414 pp., with numerous plates and illustrations. 

 (London : Frederick Warne & Co. 1901.) lis. 



The book is written as a companion to " The 

 Romance of Wild Flowers," and forms a second 

 volume in the " Library of Natural History 

 Romance." Such a title as this last cannot fail to 

 be most useful, for anything which a critic finds not 

 to be natural history may reasonaljly be ]iut under 

 the heading of romance. Any popul;ir writings, be 

 they books or articles, which, like •' Shell Life," en- 

 courage the study of living organisms, are to be 

 commended and welcomed more or less cordially 

 as they contain less or more fantastic exaggeration, 

 silly errors, and, what is e\cn worse, loose 

 writing. The first fault is not very evident in the 

 volume before ns, but one need not search to find 

 examples of the others. On p. :!0(i. for instance, 

 at which we opened the book^'^ffs'^'tatcd with 

 regai-d to the Pulmonata that ■' the members of the 

 order are distinguished by the possession of two 

 pairs of tentacles," whereas the i:iond snails of 

 which the chapter treats have but a single pair. 

 Agaiir, halfway down the second page of the 

 introduction, when we begin to read the book wo 

 find the description of the ('Ommon garden 

 snail : " The shell is packed with a solid jelly 

 of greenish hue — the living creature that formed 

 the hard shell by excretion from it.« outer sur- 

 faces — but at present it is without form, a mere 

 jelly in a jellv-mould." This, it is hardly necessary 

 to point out, is a good example of loose writing, 

 and begins to border upon the fantastic, for the 

 application of lukewarm water, we are next told, 

 causes the animal to emerge from the shell and 

 assume a definite shape in a way which makes one, 

 unwillingly perhaps, call to mind the smoke issuing 

 from a vase in the " Arabian Nights," and turning 

 into a genie of prodigious size. It seems sur- 

 prising that publishers should not submit the books 

 they decide to print to a specialist m order that he 

 may pick out inaccuracies before they are given to 

 the" public to digest. It is not our intention to 

 make up a list of the drawbacks to the volume, but 

 rather, having shown that it is not perfect, to give 

 what praise we can. The plates, which are mostly 

 '■ half-tone " reproductions from photographs of the 

 actual shells, are very pleasing examples of this 

 work, and really give an excellent idea of the 

 specimens. There is also a prodigious amount of 

 information, particularly of the interesting kind. 



