124 



NA rURE 



[December 8, 1898 



more recent investigations. Brief outlines are, how- 

 ever, given of those parts that are not especially treated, 

 in order to maintain continuity and allow of a direct 

 comparison of the properties of the ditferetit radiations. 

 Many references are given to original sources, which 

 enable the reader to extend more readily the narrow- 

 limits of the book. 



The treatise contains an account of a large amount of 

 interesting work, but it can scarcely be expected that 

 one not perfectly familiar with the subject can follow the 

 ideas so briefly expressed in many places. 



Throughout the volume we are confronted with a 

 considerable number of misleading and erroneous state- 

 ments, the nature of which can be seen from a few 

 examples. For instance, on p. 255 it is stated : — "That 

 the rays do not themselves act as conductors seems 

 proved, for they can pass between bodies of very 

 different potentials if these are not already connected 

 by lines offeree." .Any comment on this is superfluous. 



On p. 198 we read : — "The cathode rays possess the 

 same power as the ultra-violet and the \ rays, of causing 

 those gases which they traverse to become conductors of 

 electricity.' .Ml careful experiments, however, show 

 that ultra-violet light in traversing a gas does not 

 produce any conductivity. 



Again, on p. 259 it is stated that the cha rge carried by 

 the ions in X-ray conduction can be calculated from the 

 values of the saturation current and the time required 

 for the conductivity of the gas to sink tohalf of its value. 

 Such a calculation is not possible. 



On p. 254, in regard to conduction produced by the 

 passage of .\-rays through bodies, we read that " paraffin, 

 wax, sulphur, ebonite, mica, and all gases become con- 

 ductors." It is now generally believed, however, that 

 solid insulators are not made to conduct by the rays, 

 and the author ignores this side of the question. 



Strict accuracy in the facts presented is an essential of 

 every scientific treatise, as the harm produced by the 

 inception of erroneous ideas cannot be over-estimated. 



J.Z. 



Four-Jooted Americans and their Kin. By Mabel 

 Osgood \f right. Pp. xv -I- 432 ; illustrated. (London: 

 Macmillan and Co., Ltd. New York : The Macmillan 

 Company, 1898.) 

 \Vh.\tevkr difference of opinion may obtain as to 

 whether the title of this little volume is the best that 

 could have been found, or whether the "Mr. Barlow" 

 style of "Sanfordand .Merton" is the most suitable for 

 popular natural history, there can be no hesitation in ac- 

 cording the highest praise to the exquisite illustrations 

 which form its most attractive feature. In addition to 

 being in every w-ay artistic productions these, so far as we 

 can judge, are absolutely life-like ; portraying the animals 

 not only among their natural surroundings, but also in 

 characteristic attitudes. Where none are bad, and all 

 attain a high standard of excellence, it is almost invidious 

 to make a selection ; but two of the illustrations which 

 especially strike our fancy are the wood-hare on p. 141, 

 and the little striped skunk on p. iSi. It is rare, 

 indeed, to meet with illustrations of such a high 

 class, and these alone ought to give the book a large 

 sale; while the artist, Mr. E. S. Thompson, ought to 

 obtain a world-wide reputation as a delineator of animal 

 life. 



But it is not on the illustrations alone that the book has 

 to depend for popularity ; as, allowing for certain pecu- 

 liarities in the style, the descriptions of the habits of the 

 various animals mentioned are for the most part well 

 written and entertaining. A classified synopsis at the 

 end gives a clue to the identification of the species de- 

 scribed ; and in this connection it is important to notice 

 that in nearly all cases the author is thoroughly up to 

 date as regards nomenclature. As changes in nomen- 



NO. I 5 19, VOL. 59] 



clature have been necessary, it is most desirable that thej' 

 should oc adopted by popular writers. We must, how- 

 ever, take leave to object to the title of " Beef or Meat 

 Family " for the iiovidai\ as also of " .Antelope Family '' 

 for the Prongbuck, and of " Leapers" for the Leporidaa. 

 Since, too, the Viverridae are conspicuous by their 

 absence in .America, the misnomer of " Civet-cat " is de- 

 cidedly objectionable for the Cacomistle {Bassariscus}, 

 whose inclusion among the "Cousins of Cats" is scarcely 

 warranted hy the facts. .As a Christmas present to all 

 young persons interested in animals, the work may be 

 confidently recommended. R. L. 



Electricity made Easy, by Simple Language and Copious 

 Illustration. By Edwin J. Houston, Ph.D., and 

 .Arthur E. Kennelly, Sc.D. Pp. 348. (London : Swan 

 Sonnenschein and Co., Ltd., 1898.) 



SiMHLK descriptions and explanations of electrical appli- 

 ances met in every-day life are given in this volume. 

 Facts with regard to the nature and functions of electric 

 mains, the distribution of currents, generating stations, 

 the principles of incandescent and arc lighting, measure- 

 ment of electric supply, electric bells, telegraphy, tele- 

 phones, and other things concerned in the production 

 and uses of electricity are stated in the simplest of words. 

 Illustrations are given of the external and internal appear- 

 ance of many of the appliances described. These pictures 

 are, perhaps, a trifle too numerous, for they tend to give 

 the volume the character of a catalogue of electric 

 fittings. 



The comparison of the flow of water with the flow of 

 electricity is a useful one ; but there is a danger that 

 the reader will carry the analogy too far. On p. 30, for 

 instance, we read that electricity " flows through wires 

 very much like water or gas flows through pipes, but 

 flows through a solid wire as readily as through a tubular 

 wire of the same weight." Brief statements of this kind 

 are frequently the cause of serious misconceptions as to 

 the nature of electricity. 



Differential and Integral Calculus for Technical School' 

 and Colleges. By' P. A. Lambert, M.A., .Assistant- 

 Professor of Mathematics, Lehigh L'niversity. Pp. x 

 -(- 245. (New York : The Macmillan Company. 

 London : Macmillan and Co., Ltd., 1898.) 



The first hundred pages of this book are occupied with 

 the differentiation and integration of simple algebraic 

 functions, including easy applications to geometry, and 

 here and there a mechanical problem is set amongst the 

 examples. 



Then come chapters involving trigonometrical func- 

 tions, and logarithmic and exponential functions, followed 

 by a chapter containing applications to mass centres and 

 moments of inertia. The next two chapters deal with 

 expansions and applications of Taylor's thtoreni, and the 

 last forty pages of the work are devoted to an out- 

 line discussion of certain simple classes of differential 

 equations. ' 1 



There are some good features in the book considered. I 

 as an introductory text-book for ordinary school use I 

 where a good deal of supplementary oral teaching would I 

 be given. Thus the statement of methods and the I 

 proofs, or indications of proof, are clearly worded ; the ■ 

 examples are easy and straightforward, and in two or 

 three cases distinctly fresh illustrations appear. 



But the general treatment is very superficial : far too 

 much ground is covered ; there is an appearance of easy 

 progress produced by the avoiding of the real difficulties 

 which occur in the piactical applications of the calculus. 

 In fact, it is (|uiie misleading to describe the work as 

 specially adapted for technical schools and colleges. No 

 instructor of an English technical class would consider 

 this handbook an adequate introduction to the application 

 of the calculus to physics or engineering. 



