Ot-TOBER 9, 1903.] 



SCIENCE. 



471 



ume thws exteiuis tlie work begun by Kotli ami 

 brings it down to the year 1900, while ap- 

 pendices which will be issued from time to 

 time will serve to keep the work up to date. 

 It is, however, much more valuable than Roth's 

 tables in that the analytical work embraced 

 by it is of a better average quality than the 

 older analytical work and because the anal- 

 yses collected are not all thrown together 

 irrespective of quality, but are divided into 

 two classes ; the ' Superior Analyses,' which 

 judged by the various criteria discussed are 

 believed to be correct, and ' Inferior Analyses,' 

 which are of such a character that deductions 

 based upon them must be regarded as errone- 

 ous. 



The number of analyses published during 

 the seventeen years in question and which 

 are thus included in Dr. Washington's book 

 is no less than 2,881. These are rated as ' ex- 

 cellent,' ' good,' ' fair,' ' poor,' ' bad.' The three 

 first divisions being groupetl as superior anal- 

 yses are thus worthy of use in petrographical 

 discussion, while the ' poor ' and ' bad ' anal- 

 yses are classed as inferior analyses and 

 are considered to be of little or no value. The 

 superior analysis constitutes 64.70 per cent, of 

 the whole, and the inferior analysis, 35.30 per 

 cent. ; ' in other words, more than one third 

 of all the analyses which have been made in 

 the seventeen yeai-s included by the collection 

 are not worthy of use for general purposes and 

 a very large part of them are useful for no 

 purpose at all.' 



As Dr. Washington points out, petrogra- 

 phers have hitherto not been by any means 

 sufficiently exacting in the standard required 

 in rock analyses. The fact has not generally 

 been recognized that the complete and ade- 

 quate analysis of a rock is one of the most 

 complex and, in some respects, one of the most 

 difficult problems of analytical science, far 

 beyond the capabilities of a novice and de- 

 manding not only chemical knowlo<lge and 

 manipulative skill, but often the exercise of 

 considerable judgment derived from experi- 

 ence in solving the perplexing problems 

 which may present themselves. A very large 

 proportion of all the analyses which can be 



classed as 'excellent' are the work of the chem- 

 ists of the United States Geological Survey, 

 which shows the i)recniincnt position which 

 they hold in this branch of the science, while 

 the analyses that are now being made by the 

 CJeological Survey of New South Wales are 

 (if almost equally high standard. 



In the ease of each of the superior analyses. 

 Dr. Washington has calculated the norm, 

 which represents in the aggregate a colossal 

 amount of labor, but the results well repay 

 the labor expended to attain them, for all the 

 rock analyses in recent years are thus placed 

 in their proper ]>osition in the quantitative 

 system and the suitability of this system of 

 classification is demonstrated. The exact 

 rating and relative value of each analysis is 

 also given. The book may thus be regarded 

 as a sequel to the ' Quantitative Classification 

 of Igneous Rocks ' which was reviewed in 

 ScTENXE last February. It tests and illus- 

 trates in the most elaborate manner the 

 classification therein proposed. One of the 

 most valuable and interesting portions of the 

 work is that dealing with the errors which are 

 likely to vitiate rock analysis, and how they 

 may be avoided, as well as the methods of 

 judging of and testing the accuracy of an 

 analysis when it has been made. 



The book is one of the most important 

 contributions to petrography which has been 

 made for many years, and petrographers are 

 deeply indebted to Dr. Washington for the 

 wide lines on which his book is based and the 

 thoroughness with which it is elaborated. It 

 is a work which gives to the chemical aspects 

 of petrography a new significance. 



Fr.\xk D. Adams. 



McGiLL UNiYEBerry. 



DISCUSSION AND OORHESPOXDENCK. 



STATEMENTS REO.^RUINO E.\CH.\N"GES OFFEIIED BY 

 THE ALLEGHENY OBSERVATORY LIBRARY. 



While engage<l in rearranging and- classi- 

 fying the books and pamphlets of the Al- 

 legheny Observatory library we found that 

 many of our important files of the publica- 

 tions of other observatories and scientific so- 

 cieties were broken and incomplete, but that, 

 cm the other hand, we possessed many dupli- 



