1882 .] 
461 
[Merrill* 
“ altered andesites containing much secondary quartz.” 1 With the 
exception of No. 195, which is a very much altered rock, difficult 
to determine, all of these numbers seem to me to be typical, ordi- 
nary diabases. Nos. 191 and 192 with their abundant fresh augites 
besides the altered ones, with fresh large plagioclases, seem to me 
to be truly fine diabases. The whole habitus of these rocks is 
not at all, as I think, that of andesites which have been simply 
altered. 
Mr. Wadsworth considers that Nos. 196, 197, 198, 199 are 
unaltered basalts and that they form a common series with the 
rocks called by Zirkel basalts, Nos. 551 and 556. I agree with 
Mr. Wadsworth upon this point. In my first paper (p. 240, 
note 1) I remarked that Nos. 198 and 199 might be regarded as 
basalts as far as microscopical evidence alone was concerned, 
although I think that No. 198 reveals no glassy or globulitic base. 
Of these four numbers No. 196 seems to me to be more like a 
diabase than the others in its habitus. Nos. 197 and 199 I con- 
sider to be very similar to basalt No. 551 (of the Report) and 
No. 199 is undoubtedly identical with it. Both the “ basalt” No. 
551 and the “diabase” No. 199 have the same locality, Tu Tib 
Peak, Truckee Range, on their labels. No. 198 seems to me to be 
a true basalt though not identical with Nos. 197 and 199. It is 
called a' diabase in the Report, p. 99. 
Mr. Wadsworth now admits No. 200, 201 and perhaps No. 202 
of the diabases of Zirkel’s Report to be diabases but he adds : 
“ The terms melaphyr and diabase are used by me to indicate 
altered, and therefore generally old, basalts. 2 
Concerning the melaphyrs, only one need be mentioned since 
Mr. Wadsworth now admits the others to be melaphyrs. 3 
The melaphyr, No. 209, of the Report, Mr. Wadsworth calls 
an altered andesite and thinks that the larger crystals and black- 
ish grains which Zirkel ascribes to augite come from hornblende. 4 
The section shows a great many of these separations which are 
pale-green as Zirkel mentioned, and since many of these, 
which are of various sizes, show very handsomely the character- 
1 These Proceedings, Vol. xxi, p. 258. 
2 Ibid.,p. 259. 
3 Ibid., p. 260. 
4 Ibid., p. 260. 
