April 12, 1918] 



SCIENCE 



369 



for tlie great increase in size of the present 

 volume as compared with that of Professional 

 Paper 99 which appeared from the pen of Dr. 

 "Washington in 1903, and which contained the 

 analyses published up to that date. 



Xot only has the number of analyses pub- 

 lished in recent years increased but the quality 

 of the analyses has improved greatly — this 

 may be seen if the more recent analyses are 

 critically examined by the standards set forth 

 by Dr. Washington, and it is especially notice- 

 able that the quality of the analyses published 

 in the United States, Great Britain, Canada, 

 Australia and France, is now excellent, while 

 the German analyses show a dead level of 

 mediocrity. 



This improvement is to be attributed in no 

 small measure to the influence of Dr. Wash- 

 ington himself, since in his papers he has con- 

 tinually pointed out and insisted upon the 

 necessity for greater care and thoroughness in 

 rock analysis. In Dr. Washington's book on 

 Mineral Analysis, improved methods especially 

 adapted to the analysis of rocks have been de- 

 scribed and explained. It may be mentioned 

 in this connection that within the last few 

 months his remarkable skill as an analyst of 

 this class of materials, has been put to very 

 practical account in connection with the strik- 

 ing investigations which have been carried to 

 such a brilliant conclusion by the stafi of the 

 Geophysical Laboratory at Washington, in the 

 manufacture of optical glasses required for 

 the use of the United States Army and Navy. 

 All of these glasses before the war were im- 

 ported, for the most part from Germany, but 

 now as a result of these researches they can be, 

 and are being, made in sufficient quantity for 

 the requirements of the service, imder the 

 direction of these gentlemen, in certain fac- 

 tories in the United States, a new industry 

 having thus been established in this country. 



The analyses assembled in this great col- 

 lection are arranged in their proper order, ac- 

 cording to the position of their "norms" in 

 the Quantitative Classification. In each case 

 not only is the analysis itself reproduced, but 

 the " norm " is also given (the " norms " of 

 the whole 8,602 rocks having been re-calculated 



and verified by Dr. Washington), as well as 

 the locality, analyst, literature reference, and 

 the name by which the rock is described by the 

 author. 



The analyses are arranged in four parts. 

 Part I. embraces the " Superior Analyses of 

 Fresh Pocks " and makes up the greater part 

 of the volume. This is followed by Part 11., 

 which includes the " Superior Analyses which 

 are Incomplete through the Non-determination 

 of Some One or More Constituents." Part 

 ni. sets forth the " Superior Analyses of 

 Weathered or Altered Rocks and Tuffs," while 

 in Part IV. are gathered " Inferior Analyses " 

 embracing those which are poor or bad. 



The only errors to which attention is called 

 are on p. 720, where in the Jacupirangite of 

 Brazil the silica content should be given as 

 38.38 -per cent, instead of 58.38 per cent, and 

 on p. 1197, line 2, left column, where the cap- 

 tion British Guiana is omitted. 



An excellent description of the Quantitative 

 Classification itself, a tabular presentation of 

 the divisions of names of the Quantitative 

 Classification, the method of the calculation 

 of the norm, together with tables of the molec- 

 ular numbers and of the percentages of the 

 norm molecules, are presented in five short 

 appendices. It would subserve a very useful 

 purpose if these appendices were reprinted 

 separately, since they could be used much 

 more readily in the form of a pamphlet of 

 30 pages than as part of the present massive 

 tome embracing 1,200 pages. The reviewer 

 hopes that the authorities of the United 

 States Geological Survey will view favorably 

 the suggestion that these appendices be is- 

 sued as a separate paper. 



Geologists will look forward to the discus- 

 sion of " The Distribution of Magmas " and 

 " The Average Rock " which are to be made 

 the subjects of separate papers by the author, 

 to appear later. 



The excellent indexing of the volume and 

 the high character of the press work are worthy 

 of especial mention. 



It is a volume which must find a place on 

 the shelves of every petrographical laboratory 

 in the world. 



