Zirkel.] 114 [November 1, 



The question whether propylite is a " distinct species " or merely 

 a "variety" has ever been and still is a totally unessential point 

 for me, and I do not wish to argue about that with Mr Wads- 

 worth, maintaining my opinion (with his permission) that the 

 rocks in question may be readily distinguished from true ande- 

 sites. 



11. Mr. Wadsworth need not doubt that I was sufficiently 

 familiar jwith the strange prussian-blue grains which so often 

 occur on the surface of the thin sections in the Canada balsam, 

 long before he began to study rock sections at all, and that I 



have not mistaken them for hauyne. Had I done so, I should 

 have had to quote hauyne as an ingredient of many hundred of 

 the Fortieth Parallel rocks, instead of quoting it in only two of 

 them. If Mr. Wadsworth will study the sections Nos. 300 and 

 and 301 with a little more care, he will find (perhaps accompanied 

 by the other blue grains — impurities — of which I have taken 

 no account whatever) those little blue crystals in the groundmass 

 and in the feldspars, which I have supposed to be hauyne ; he 

 will succeed the easier and better, the more his knowledge of 

 European hauyne-bearing rocks is advanced. 



12. Concerning the quartz in the rhyolite from the north end 

 of Wachoe Mts. (vi, p. 197), which contains fluid inclusions, if 

 this quartz belongs to an included fragment of granite, as I have 

 supposed and as Mr. Wadsworth has confirmed, it has nothing to 

 do, of course, with the rhyolite itself, and Mr. Wadsworth has 

 no right to complain of any inconsistency between my statement, 

 that rhyolitic quartzes carry glass inclusions only and the 

 assignment of this rock to the rhyolites. Specimen No. 201, in 

 which some of the primary quartzes bear fluid inclusions, I have 

 assigned on this very account to the trachytes and not to the rhy- 

 olites (the entire habitus of the rock was not at all propylitic) - 

 in accordance with my statement quoted by Mr. Wadsworth, that 

 all tertiary quartziferous rocks, other than propylites, *". e. dacites 

 and rhyolites, contain only glass inclusions in their quartzes. In 

 other words, the fact that the quartz of this rock carried fluid 

 inclusions, was to my mind, a more important diagnostic distinc- 

 tion, than the fact itself, that the rock carried quartz and was 

 otherwise rhyolitic. I think that this would appear plain to the 



