Wadsworth.] 
266 
[October 19, 
ments, and therefore belonging with Zirkel’s clastic rocks. Nos. 
277 (897), 278 (1783) I hold are fragmental rocks, of which the 
latter at least is old. They both appear to be formed from rhyo- 
litic (felsitic) debris. The remainder are considered by me, with 
but one exception, to be rhyolitic (including felsitic) rocks of vari- 
ous ages. No. 279 (1852) is the exception. This I hold is an old 
andesite containing quartz as an alteration product, and would 
therefore be the only dacite, properly so-called, according to 
King and Zirkel’s definition. Since the rock is an altered ande- 
site, and the quartz a secondary product, there seems to be no 
use for the term dacite here to indicate a quartz-bearing andesite, 
unless secondary minerals are to be raised to the same rank in 
nomenclature that original ones hold ; and in this case the rock is 
the same as the only real quartz-propylite, i. e. an altered ande- 
site. We thus have two names to indicate the same thing. 
Trachytes. 
Nos. 289 (293), 323 (2589), 324 (2611), 325 (2601), 327 (2616), 
329 (2617), 330 (2620), 332 (2621), I hold are both macroscopic- 
ally and microscopically basalts, and except one or two which are 
allied to the andesites, are well marked basalts. These in part 
belong to the same series as No. 612 (2619) a resemblance, which 
Professor Zirkel also noticed (YI, pp. 161,251 ; II, pp. 169-173). 
The number of the rock 612 (VI, p. 251) is erroneously given as 
328 on page 161 of Zirkel’s report. It should be noticed here 
that while Zirkel states that this rock contains no olivine, this 
mineral can be seen in the section in considerable quantity (VI, 
p. 251). The quartz, except some alteration quartz, observed 
by Zirkel in these rocks, is held by me to be of prior origin to 
the consolidation of the basalt, that is, it is foreign to the rock. 
However, had these rocks been assigned to their proper species, Mr. 
King might out of them have made his quartziferous division of the 
basalts, and not plunged the rhyolites into the basaltic lake as he 
has done. It is further thought that the analyses of two of the 
above rocks (the only two analyzed) given in Table X of King’s 
report (Analyses 143 and 144) bear out my views as to their 
relation. 
