90 GEOLOGY OF THE COMSTOCK LODE. 



subject of this paper. Nevertheless, I have given my notes upon them in 

 the section containing the "Detailed description of slides." There appear 

 to be fairly good grounds for the determinations there suggested, and the 

 specimens seem to oflfer no evidence even approximately sufficient for the 

 establishment of a new rock-species. 



No propyiite yet found in the United States. — The term propylite might bo retained 

 to express a certain macroscopical appearance and certain chemical changes, 

 just as we still speak of serpentine without denying its secondary character. 

 But a better name, and an older one, already exists for this very thing, for 

 the terms greenstone and greenstone-trachyte designate rocks in every way 

 similar. Considered as its originator intended it, as a pre-andesitic Tertiary 

 rock, I feel no hesitation in asserting that nothing answering to its defini- 

 tion has as yet been proved to exist in the United States.^ 



' European propy lites. — The investigation of American propy lites described in this report was carried 

 out entirely without reference to the opinion of European lithologists regarding the Transylvanian 

 rocks. American geologists who have not followed the subject closely may be interested to learn, how- 

 ever, that the tendency of opinion in Europe is strongly against the independence of this rock-sj)ecies. 

 Dr. C. Doelter upholds it in a paper " Ueber das Vorkommen des Propylits in Siebenbiirgen. Verhandl. 

 der k. k. Geolog. Eeichsanstalt," 1875, p. 27. In reviewing this paper in the "Neues Jahrbuch fiir Miu- 

 eralogie," etc., 1871), p. G48, Profes.sor Rosenbusch incidentally considers Baron v. Richthofeu's descrip- 

 tion and Professor Zirkel's views, and states his own conclusions as follows (translated): 



" The reviewer, iu common with all other investigators, willingly recognizes the peculiar green- 

 stone habitus of the so-called jiropylites ; their Tertiary age, which in many cases must be further and 

 more sharply determined, being assumed. Since similar changes in habitus occur in many other series 

 of rocks, however, ho does not feel himself compelled to accord propylite an independent position, but 

 rather to regard it as a mere pathological variety of quartzose or quartzlesa homblende-andesites, or of 

 the augite-audesites, as the case may be." 



Professor vom Rath has jmblished a paper in the " Sitznngsberichte derNeiderrheinischen Gesell- 

 schaft in Bonn," vol. 35, 1878, p. 26, in which he expresses a very positive opinion that the so-called 

 propylite of Schenmitz is diabase, and has no relation to the andesites of the neighborhood. He as-'serts 

 that this diabase has a very different look macroscopically and microscopically from andesites, but it is 

 to be regretted that he dors not give the differences in sufficient detail to enable readers to judge for 

 themselves. Prof. J. Szab6 has read a paper before the Hungarian Geological Society, which i.s 

 reported in the Verhandlungen der k. k. Geolog. Reichsaustalt, 1879, Literatumotizen, p. 17. In this 

 paper Professor Szab(5 maintains that various eruptive rocks and even sedimentaries have been altered 

 to what is called greenstone by solfataric action at Schemnitz, and he concludes with the following 

 statement (translated) : "There is no greenstone-trachyte formation proper in a geological sense ; there 

 has never been an independent propylite eruption." I infer that the conditions in Schemnitz are sab- 

 Btantially similar to those iu Washoe. 



