368 



SCIENCE 



[N. S. Vol. XLYII. No. 1215 



the use of carbon copies. Do you care to join 

 them? 



We have no record of the translation of the 

 paper by 



In accordance with your request we will keep 

 your application on file. 



If the requests for this translation number 



or more before (date) 



(no.) others have agreed to share in the 



cost of having a translation made. Do you care 

 to join them? 



Are you willing to translate the paper or see 

 that it is translated on this basis? 



has agreed to translate this paper 



and to forward a copy to you. 



This scheme of exchanging translations of 

 papers in geology and paleontology is described 

 in Science for April 12, 1918. It is available 

 to all and depends for its success upon your co- 

 operation. Lancaster D. Burling 



Geological Subvey, 

 Ottawa, Canada 



SCIENTIFIC BOOKS 



Chemical Analyses of Igneous Rocks. Pub- 

 lished from 1884 to 1913 inclusive. With a 

 critical diseussion of the character and use 

 of analyses. By Henry Stephens Wash- 

 ington. U. S. Geological Survey, Profes- 

 sional Paper 99, Washington, 1917. 

 The Quantitative Classification of igneous 

 rocks is one of the many very important con- 

 tributions which America has made to the 

 science of geology. As is well known it is the 

 product of the labors of four distinguished 

 petrographers — Professor Iddings, Professor 

 Pirsson, Dr. Whitman Cross and Dr. H. S. 

 Washington — and is based on the chemical 

 composition of rocks rather than on their 

 mineralogical character which formed the 

 basis for the various older classifications. 



In the earlier years of geological science 

 but little attention was paid to the chemical 

 composition of rocks, except in a very general 

 way. Later when the chemical analysis of 

 rocks came to be more common, the analyses 

 were carried out in a very careless way since 

 the rocks were considered to be merely aggre- 

 gations of certain minerals the relative pro- 

 portions of which might vary more or less, 

 and, consequently, the chemical composition 



of the whole would be represented with suffi- 

 cient accui'acy even although an error of a 

 per cent, or two in any one or other of the 

 chemical constituents might be made. Now, 

 however, the study of these igneous rocks is 

 regarded as a study of silicate solutions and 

 their equilibria and the subject has thus be- 

 come a special branch of physical chemistry. 

 Such being the case the accurate chemical 

 analysis of igneous rocks is recognized to be 

 of the greatest importance, and the correct 

 understanding of the composition of these 

 rocks is now seen to have a very far-reaching 

 and important bearing on some of the most 

 fundamental problems of the science. 



As the importance of the chemical compo- 

 sition of rocks became increasingly recognized, 

 attempts were made to collect and correlate 

 all published analyses. The most notable of 

 these was that of Justus Roth whose " Tabel- 

 len " of rock analyses were published by in- 

 tervals between 1869 and 1884, and the more 

 recent collection of A. Osann. 



The present work by Dr. Henry S. Wash- 

 ington of the Carnegie Institution, Washington, 

 goes far beyond these. Every serial whether 

 published by a Survey, Society, or other organ- 

 ization, which might conceivably contain pet- 

 rographic material, has been examined vol- 

 ume by volume, the examination embracing 

 publications from the year 1883 to 1915. As 

 all the analyses of importance published before 

 1883 had already been collected by Roth and 

 are embraced in the present list — and as Dr. 

 Washington has spared neither time nor effort 

 to include in his paper all analytical material 

 which is worthy of consideration — the present 

 collection of analyses may be said to be com- 

 plete, perfect and final. To use a colloquial 

 expression the volume under review is " the 

 limit." 



The total niunber of analyses tabulated by 

 Dr. Washington amounts to no less than 8,602, 

 and it is significant of the increased interest 

 taken in rock analysis in recent years to note 

 that in the thirteen years from 1901 to 1913 

 inclusive, nearly twice as many analyses were 

 published as during the sixteen preceding 

 vears between 1884 and 1900. This accounts 



