Chemistry and Physics. 605 



slight traces of hydrogen have always made their presence 

 known. The negatives taken by Curtis (removed by enlistment) 

 have been recently studied by A. Fowler w T ith the result that 

 some remarkable facts have been revealed. The spectrum com- 

 prises, among other things, bands with single heads and bands 

 with double heads, all of which are degraded towards the red. 

 The present paper relates only to the bands having two heads. 



The important facts brought out by the preliminary study of 

 the plates may be summarized as follows : (1) The doublets do 

 not follow the ordinary law of band spectra, but can be arranged 

 in two series of the type hitherto exclusively associated with line 

 spectra, and can be approximately represented by the usual 

 formulae involving the Rydberg constant. Nine bands of the 

 main series and four of the fainter second series have been 

 identified. (2) The two series may be likened to the Principal 

 and Diffuse series in the case of line spectra, but the usual relation 

 between such series is not certainly indicated, and no equivalent 

 of the Sharp series has yet been traced. (3) The doublet 

 separations are not in accordance with those associated with line 

 spectra ; they diminish in passing along the series, but do not 

 vanish at the limit. —Proc. Roy. >$oc., vol. xci (A), p. 216, March 

 1915. h. s. u. 



II. Geology. 



1. Problems of American Geology, by William North Rice, 

 Frank D. Adams, Arthur P. Coleman, Charles D. Walcott, 

 Waldemar Lindgren, Frederick L. Ransome, William D. 

 Matthew. A series of Lectures Dealing with Some of the 

 Problems of the Canadian Shield and of the Cordilleras, Delivered 

 at Yale University on the Silliman Foundation in December, 

 1913. Pp. xvii-f505, pis. 7, figs. 63, maps and diagrams 4. 

 Yale University Press, 1915. — This volume of lectures was 

 planned to commemorate the centennial of the birth, in J 813, of 

 James Dwight Dana, and the semi-centennial of the publication in 

 1863 of the first edition of his most important work, the Manual 

 of Geology. As Dana was so eminent a geologist, the Geological 

 Department of Yale University desired that the lectures should 

 be of high scientific attainment. It was furthermore held that 

 the best form of commemoration was to contribute the results of 

 new researches on subjects of present vital interest ; subjects 

 which are an outgrowth of the interests of the previous generation, 

 rather than to plan a review of past accomplishments. The 

 completed volume shows the value of this point of view. 



Professor Rice presents 'an introductory chapter on " The 

 Geology of James Dwight Dana." He shows the great advances 

 in philosophic concepts in geologic science which were made by 

 Dana and also the corrections in certain points of view which 



