1881.] 
269 
[Wadsworth. 
(1446), 423 (1471), 473 (2063 J, 491 (572), 492 (809), etc. Zirkel 
calls the andesitic fragments in No. 492 (809) “ felsitic rhyolite.” 
No. 473 (2063) is said to contain no biotite , but it does hold bio- 
tite that can be seen not only with the microscope but also with 
the naked eye (YI, p. 196). The “pieces of dark-gray rhyolite,” 
b in 479 (2130), are apparently fragments of a melaphyr, but it 
is somewhat doubtful if the section came from Col. No. 2130. 
Nos. 364 (870) and 367 (878) are regarded by me as ande- 
sites ; 365 (872) is too much decomposed to be sure about it, but 
I consider it to be a decomposed basaltic rock, as is also apparent- 
ly Col. No. 868, although no section of it could be found. Col. 
No. 868 and Nos. 365 (872) and 366 (875) are said on the labels 
to overlie the basalt. Col. No. 875 is a rhyolite, hence here is an 
exception to Richthofen’s law although King says he found none. 
The section No. 380 (948) is probably not from hand S23ecimen 
948. Rhyolite No. 384 (980) is the same as the chalcedony No. 
656 (980), (YI, pp. 177, 271). 
No section of No. 386 (913) could be found by me, but the hand 
specimen is evidently a basalt. No. 423 1 (1518) is evidently an 
andesite, as Emmons suggests, containing a fair amount of plagio- 
clase, but none of the quartz it was said to hold by him could 
be found by me (I, p. 188, II, p. 642). No. 467 (1876) is held to 
be a fragmental rock. 
The divisions into which Zirkel has separated the rhyolites are 
not regarded by me as natural ones, since no line can be drawn 
between them except an arbitrary one. Mr. King is mistaken in 
his statement that the “ nevadite ” has only slight traces of “ vit- 
reous binding material” (I, p. 722). It is furthermore true 
that many of the porphyritic and felsitic rhyolites contain less 
glass than the “nevadites.” 
The quartz found in the rhyolitic groundmass is regarded by 
me as a devitrification product, and therefore not a suitable min- 
eral to found lithological species upon (II, p. 463). 
On page 117 of Yol. VI, Professor Zirkel in speaking of the 
fluid inclusions in the quartz of No. 226 (1641) stated : (The italics 
are mine.) “As respects this point, indeed, the quartz of this 
This in Vol. vi is a misprint for 433, since No. 423 occurs on page 186. 
