I02 



NATURE 



[Dec. 5, 1889 



genus) have been reproduced, intercalated in the text, in 

 a manner which is highly creditable to the Lithographic 

 Etching Company. 



Considering how much remains to be done in the in- 

 vestigation of the fish-fauna of India and its British 

 dependencies, it is a matter of regret that so httle atten- 

 tion has been paid to the subject since Mr. Day's depar- 

 ture from India. The supplement to the " Fishes of 

 India," published in 1888, records no more than sixty 

 additions to the number of species, a figure which might 

 easily have been doubled in the same lapse often years but 

 for the unaccountable want of interest shown in this most 

 important branch of study. As an example of the results 

 which may be attained by an enthusiastic collector in 

 those regions, we may allude to the collections of fishes 

 brought together during the last three or four years by 

 Mr. Jayakar, a surgeon stationed at Muscat, at the 

 entrance of the Persian Gulf, and presented by him to 

 the British Museum, by which no less than twenty-five 

 species, many of large size and of commercial im- 

 portance, have been added to the record of the fishes 

 of the Indian Ocean. It is to be hoped, therefore, 

 that this new and well got up issue of the " Fishes of 

 India" in a more j)ortable form will give a fresh 

 stimulus to the study of that fauna. A little more, how- 

 ever, might have been done to facilitate the identifica- 

 tion of species, a particularly arduous task, the difficulties 

 of which would have been greatly lessened by the pre- 

 paration of satisfactory " keys." Such as they appear 

 in this work, viz. mere abbreviated tabulations of cha- 

 racters, without or with scarcely any groupings under 

 special headings, the synopses fail in their object, and it 

 is really a matter of regret that the editor did not bring 

 his influence to bear for a thorough recasting of this por- 

 tion of the work, especially in the case of such extensive 

 genera as Barbiis, Neiiiachilus, Lutjanus, or Scrranus, 

 where the work of identifying species by means of the 

 synopsis given is perfectly discouraging. With the enor- 

 mous multitude of species which our present knowledge 

 requires us to grasp, it is of primary importance that every 

 possible facility should be given to the naturalist who uses 

 a manual of this kind, which after all is intended chiefly 

 for those who have but an elementary knowledge of the 

 special subject. 



The above notice was in type when we received a copy 

 of the second and concluding volume (509 pp., 177 figs.). 

 We are glad to see that the editor has, in many cases, 

 recast the synopsis of genera and species. The total 

 number of fishes known from Indian waters is given as 

 1418. 



In concluding, we congratulate Mr. Blanford on having, 

 under difficult circumstances, so successfully brought out 

 this portion of the " Fauna of India" ; and we join in his 

 tribute to the memory of the late author, who, as he justly 

 says, has rendered signal service to Indian zoology. 



OUR BOOK SHELF. 



La France Prihisioriquc. Par Emile Cartailhac. (Paris: 

 Felix Alcan, 1889.) 



This volume forms one of the well-known series, 

 " Bibliotheque Scientifique , Internationale," published 

 under the direction of M. Em. Alglave. The subject, 



we need scarcely say, is one with which M. Cartailhac 

 is eminently competent to deal, and all who are inter- 

 ested in the study of prehistoric times will be glad to 

 have so compact and lucid an account of the facts to 

 which the work relates. He begins with a good sketch 

 of the rise and progress of modern ideas with regard to 

 primitive civilizations and the antiquity of the human 

 race ; and this is followed by a discussion of the ques- 

 tions connected with man's place in Nature, his origin, 

 and the supposed traces of his existence during the Ter- 

 tiary period. An admirable chapter is devoted to the 

 striking manifestations of artistic impulse by men of the 

 Palaeolithic age. The monuments of the Neolithic era 

 in France are grouped with perfect clearness, and M. 

 Cartailhac has not failed to do justice to any one of the 

 various questions which these monuments have forced 

 upon the attention of students. The scientific value of 

 the book is enhanced by the fact that he avoids as much 

 as possible the use of purely hypothetical reasoning. 

 When he comes to sets of phenomena which cannot be 

 simply and naturally accounted for, he thinks it better to 

 offer no theory at all than to suggest purely conjectural 

 explanations. The illustrations, although in no way re- 

 markable, will be of considerable service to readers who^ 

 have not made themselves familiar with the aims and 

 methods of archaeological science. 



Experimental Science {Elementary, Practical, and Ex- 

 perimental Physics). By George M. Hopkins. (New 

 York : Munn and Co. London : E. and F. N. Spon,. 

 1890.) 



The subject of experimental physics is here set forth in 

 a manner calculated to aflbrd to the student, the artisan, 

 and the mechanic, a ready and enjoyable method 

 of acquiring a knowledge of this fascinating subject. 

 Although the popular style adopted by the author per- 

 haps makes the book better suited to the general reader 

 than to the student, it may safely be said that all classes 

 of readers will find much to interest them. All the 

 subjects usually included in the comprehensive term 

 "physics-' are discussed ; and, in addition, photography, 

 microscopy, and lantern manipulation. By carefully 

 performing each experiment at the time of writing the 

 description, the author guarantees certain success if his 

 instructions are followed. There is an excellent chapter 

 on " mechanical operations," containing many valuable 

 hints on glass working, simple apparatus for laboratory 

 use, soldering, and moulding. ?*lathematical expressions 

 are almost entirely excluded. 



The book is chiefly remarkable for its hundreds of ex- 

 cellent illustrations, very few of which are diagrammatic. 

 Many of them, like a considerable portion of the text, 

 have already appeared in the Scientific American, which 

 is alone sufficient guarantee of their quality. Some of 

 the latest inventions, including Edison's new phonograph,, 

 are desciibed and illustrated. 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents . Neither can he undertake 

 to return, or to correspond with the writers of, refected 

 manuscripts intended for this or any other part of Nature, 

 A'o notice is taken of anonymous cotntnunicaiions.^ 



" Modern Views of Electricity." 



The only point really at issue between Prof. Lodge and 

 myself seems to be whether the difference of potential between- 

 two metals in contact can be measured by the Peltier effect or 

 not. He asserts that he regards the statement that it can as an 

 axicm, while 1 maintain that the only reason for calling it an 

 axiom is that it cannot be proved. Let us take a simple case. 

 Suppose we have a condtnser, the plates of which are made of 

 two different metals metallically connected, and that this con- 



