468 Scientific Intelligence. 



bodies in movement and of which the principles are those of 

 Hertz, of Lorentz, and of Larmor. 



Very interesting, as giving an insight into the intellectual atti- 

 tude of the author, and well worth quoting, are the following 

 paragraphs from his preface : — 



u Although none of these theories seems to me entirely satis- 

 factory, each of them contains without doubt a portion of truth 

 and a comparison may be instructive." . . . " Of all, that of 

 Lorentz appears to me to correspond most nearly with the facts." 



He adds that it is possible that the recent investigations of 

 Cremieu, should they be confirmed, may completely alter our 

 ideas concerning the electrodynamics of bodies in movement. 



Doubtless the instructed student of electricity will turn with 

 the liveliest interest to Part Third of the book, which is given 

 to the discussion of the merits and defects of the latest theories 

 of electricity. It is quite impossible to give here even the barest 

 outline of a review which occupies nearly three hundred pages of 

 most acute criticism presented with almost unexampled clearness 

 and with a mastery of analytical methods which few scholars will 

 be able to fully comprehend without strenuous effort. The 

 author's exposition of the various theories which he is about to 

 submit to critical analysis is singularly lucid and satisfactory, 

 and it offers unusual temptation for a reviewer to give numerous 

 quotations, but selection from such a wealth of examples would 

 be as difficult as to do justice in any translation. 



Part Four, consisting of a little more than fifty pages, is given 

 to a general discussion of points in electrical and optical theories 

 suggested by the recent work of Larmor. The method of this 

 part is somewhat different from that of the preceding portions 

 being more discursive and of an obviously less final form ; but 

 there is a certain charm due to these very features which the 

 reader would not willingly miss. 



As a result of a careful inspection of this work, we are impelled 

 to say that no book comparable with it as a source of intellectual 

 stimulus to the qualified student of physics or so full of sugges- 

 tiveness has appeared for a long time. c. s. h. 



II. GrEOLOGY AND NATUKAL HlSTOEY. 



1. United States Geological Survey, 21st Annual Report of the 

 Directory by Charles D. Walcott. Pp. 1-204, with 3 maps, 

 1 figure, 1900. — The total appropriations made for the fiscal year 

 1899-1900 for the work of the U. S. Geological Survey was 

 $834,240.89. The expenditure of this amount was distributed 

 over a very large field of investigations, carried on in all parts of 

 the country. The work accomplished during this year was. in 

 general, a continuation of that of previous years and with sub- 

 stantially the same organization. The Director calls especial 

 attention, in his report, to the following branches of the work, 

 viz : The survey of the Forest Reserves, the explorations in 



