856 



SCIENCE. 



[N. S. Vol. XXIV. No. 626. 



graduate students in geology, chemistry and 

 physics. But such work should follow the 

 introductory course. In this advanced course 

 a full treatment of the Miller indices, axial 

 ratios, etc., finds its proper place. Would it 

 not be the height of folly to recommend that 

 extended philological researches be introduced 

 into the beginning course of one of the 

 modern languages? At any rate. Professor 

 Rogers's statement that ' without something 

 of the sort (meaning crystal measurement, 

 calculation and drawing) the time given to 

 crystallography may almost be a waste of time 

 unless it is taken up at some future time ' is 

 to my mind altogether too sweeping and cer- 

 tainly needs qualification. I would like to 

 ask what student of mineralogy has not found 

 a course in elementary crystallography of the 

 highest value and interest, even though it did 

 not include the work supposed by Professor 

 Rogers to be of paramount importance. 



Edward H. Kraus. 



MiNERALOGICAL LABOEATOBY, 



University of Michigan, 

 November 20, 1906. 



CHAMBERLIN AND SALISBURY'S TEXT-BOOK OF 

 GEOLOGY. 



The review of the three-volume * Text-book 

 of Geology' by Professors Chamberlin and 

 Salisbury in a recent number of Science, is 

 likely to convey to the general reader an 

 erroneous impression of that publication. 

 Certain idiosyncrasies of style and little errors 

 of detail, some of which are not real, are dwelt 

 upon at such length that one becomes imbued 

 with the idea that such mistakes are abundant 

 and that they detract largely from the value 

 of the text. It is natural that in a book of 

 this size a number of things may be found 

 worthy of criticism, and especially is this true 

 of little matters which are likely to escape 

 notice in reading the proof of the first edition. 

 Mistakes of this class are better brought to 

 the attention of the authors through the me- 

 dium of a personal communication than by 

 making them the subject of complaint in the 

 public prints. Enough of such details can be 

 found in any work to convey a wrong impres- 

 sion of the whole, if they are given so large a 



space that the main features of the work re- 

 ceive subordinate notice. It should be the 

 function of a review to give the reader a cor- 

 rect understanding of the important and read- 

 able qualities of the book, whether they are 

 good or otherwise, and not simply to recount 

 trivialities. While in this case the reviewer 

 finally gives adequate expression of his appre- 

 ciation of the high value of the books con- 

 cerned, this expression is prefaced by so many 

 criticisms of details that the effect of his com- 

 mendation is largely lost. 



Some of the criticisms affect mere over- 

 sights in proof-reading, which are bound to 

 occur in any publication of this magnitude. 

 Several of these have been corrected in the 

 second edition of volume I. Such an error 

 was the use of ' syncline ' for * anticline ' as 

 pointed out by Dr. Branner. 



A large number of the specific faults men- 

 tioned in the review are found on closer in- 

 spection to be imaginary rather than real, 

 and one is forced to conclude that the reviewer 

 was somewhat hasty in his perusal of the text. 

 Of this nature is the criticism of the state- 

 ment that " theoretically the rotation of the 

 earth should increase erosion on the right 

 bank of streams in the northern hemisphere 

 and on the left bank in the southern," because 

 " no reference is made to the direction of the 

 streams," for this tendency is not dependent 

 upon the direction of the streams, and the 

 authors were correct in leaving their state- 

 ment unqualified in this particular. 



The reviewer takes exception to the state- 

 ment that the advent of the Ammonites oc- 

 curred in the Permian and cites Monograph 

 XLIL, U. S. G. S., as showing that they were 

 abundant in the coal measures. The genera 

 described in that work, however, belong to the 

 types most widely known as Goniatites and 

 Ceratites, the occurrence of which was duly 

 mentioned by the authors. These are am- 

 monoids, of course, but not Ammonites as 

 the term is generally understood. The spe- 

 cific statements of the authors are therefore 

 discriminative. 



The statement of the authors that ' differ- 

 ences in density of sea water are due to dif- 

 ferences in temperature and salinity' is criti- 



