1883.] 417 [Wadsworth. 



cepted in Europe and was not adopted by Zirkel until his visit to 

 New York, I proceed to show what grounds have been taken by 

 the United States geologists and lithologists on the points dis- 

 cussed in my previous papers. In the second annual report of 

 the Director of the United States Geological Survey, Dr. Becker, 

 going even farther than I went in condemnation of Zirkel's work, 

 states of the Washoe district, the rocks of which were studied by 

 Richthofen, King, and Zirkel : " The reduction of rocks of origin- 

 ally different aspect to apparently uniform character by chloritic 

 decomposition is strikingly evinced by a mere list of the species 

 in the district, which have been grouped under the terms pro- 

 pylite and quartz-propylite. These are granular diorite, porphy- 

 ritic diorite, diabase, quartz-porphyry, hornblende-andesite, and 

 augite - andesite. ... The ' green hornblendes ' are simply 

 pseudomorphs of chlorite after hornblende or augite as the case 

 may be. . . . The description of propylite as a species arose 

 from the erroneous determination of chlorite as green hornblende. 

 . . . The microscopical characteristics of propylite are illusory. 

 Finely disseminated hornblende in the groundmass of a Washoe 

 rock is very rare, and far rarer is the presence of particles of 

 hornblende in feldspars. . . . Base is rare in propylites ; where 

 it originally formed a constituent of the rock, it has for the most 

 part undergone devitrification. . . . There is no proof yet known 

 of the existence of a pre-andesitic Tertiary eruption in the United 

 States. The term propylite should not be retained in the nomen- 

 clature of American geology even to express certain results of 

 decomposition, for the equally loose term, greenstone, seems to 

 cover the same ground and has priority." (I. c. pp. 297, 298.) 

 Becker thus agrees with my earlier condemnation of propylite. 

 It will be remembered that objections were offered by me (B. 

 285 J to the quartz-propylites and dacites on the ground that most 

 of them were old rhyolitic rocks, in which term I included felsite, 

 quartz-porphyry, etc. Dr. Becker states of these: "The quartzose 

 rock of the district which von Richthofen had determined as a 

 pre-Tertiary quartz-porphyry, King regarded as quartz-propylite. 

 . . . Zirkel . . . confirmed the independence of propylite and 

 quartz-propylite as lithological species, regarded the quartzose 

 rock as dacite . . . This rock [the above quartz-porphyry], which 

 Baron v. Richthofen determined correctly, has since been called 



PROCEEDINGS B. S. X. H. VOL. XXII. 27 JUNE, 1-SS4. 



