678 



SCIENCE 



[N. S. Vol. XXXVI. No. 933 



along those lines of the chemistry of sanita- 

 tion in which she was interested, and the 

 other to be used in the interests of Home Eco- 

 nomics, are already of considerable size, and, 

 if still further supported, will do much to per- 

 petuate her life work. 



If the zeal of the biographer has occasion- 

 ally (though seldom) led to the use of ultra- 

 superlatives, it is far more frequently true 

 that, in the compass of such a work as this, it 

 has been impossible to do full justice to her 

 attainments in so many fields. The volume 

 is amply illustrated (the frontispiece being a 

 most excellent photograph of Mrs. Eichards, 

 taken near the close of her life) and it can 

 hardly fail to be a source of gratification to 

 all concerned with its preparation. It is a 

 book which should be widely read and from 

 which much pleasure and profit is sure to be 

 derived. 



H. P. Talbot 



The Examination of Prospects. A Mining 

 Geology. By C. Godfrey Gunther. New 

 York, McGraw-Hill Book Company. 

 This book, which is attractively bound in 

 flexible leather as a pocket manual of 221 

 pages, presents the practical side of the geol- 

 ogy of metalliferous ores, excepting iron and 

 placers. Sound advice is given on the pro- 

 cedure of the examination and sampling of 

 mines, and especial attention is devoted to the 

 outcrops and structural features of ore de- 

 posits. 



The writer states at the outset that a great 

 proportion of the deposits having outcrops of 

 commercial grade or of evident promise have 

 already been recognized and explored. Rich 

 discoveries at the surface belong to pioneer 

 days, and as time goes on the more important 

 developments are the result of lower working 

 costs, improved metallurgical processes, and 

 of an increasing knowledge of economic geol- 

 ogy. As engineers in search of developed mines 

 no longer expect to find properties having 

 positive ore of greater net value than the price 

 asked, so those in search of prospects should 

 not expect to find proved ore-shoots awaiting 

 their recommendation. There is usually lo- 



cal capital for the preliminary development of 

 a patently good prospect, and most of these 

 are steadily worked from the time of their dis- 

 covery until some apparently unfavorable de- 

 velopment shuts off the supply of local capi- 

 tal. These statements recall one frequently 

 heard that " all mines are poor at the bot- 

 tom." The basis is partly geological and 

 partly psychological, for men seldom stop dig- 

 ging when in bonanza. A great majority of 

 prospects have been examined again and 

 again, presumably by men who commanded 

 a knowledge of sampling, the services of an 

 assayer, and at least an elementary knowl- 

 edge of geology. In order to pick a good pros- 

 pect from those rejected by his predecessors, 

 therefore, an engineer must base his hope of 

 success upon superior geological training. 



Although the author does not attempt a 

 genetic classification of ores, he does present 

 in a logical and effective manner a mass of 

 carefully chosen and ably digested material. 



The treatment of the superficial alteration 

 of ore deposits and the secondary enrichment 

 of copper, silver and gold ores is concise and 

 clear; but in view of Stokes's experiments in 

 the solution of gold in ferric salts, the state- 

 ment that gold is dissolved in solutions of 

 ferric hydrate would seem to demand experi- 

 mental proof. Numerous examples are cited 

 of changes in value and character that have 

 been noted as ore lodes are followed in depth. 

 The many text figures, which are well chosen 

 and well executed, add greatly to the attrac- 

 tiveness and value of the volume, and both the 

 author and publisher are to be congratulated 

 on its appearance. 



W. H. Emmons 



Minneapolis 



SPECIAL AETICLES 



NOTE ON THE DEVELOPMENT OF AMPHIBIAN LAEVjE 

 IN SEA-WATER 



That the amphibia are poisoned by common 

 salt, and hence geographically restricted to re- 

 gions free from this substance, is a general be- 

 lief, apparently so well supported by observa- 



