76 Scientific Intelligence. 
that the two localities are in the same lithological district. He 
says that it is not necessary or possible to prove, that the pebbles 
came from the Comstock locality; and recognizes, in a following 
paragraph, the fact that the distinctions between the porphyritic 
diabase and the augite-andesite of the Comstock walls “ are some- 
what refined” and in many cases not distinguishable in hand 
specimens. Still he believes that the distinctions are sustained by 
his observations. Other arguments are presented in order to prove. 
succession in periods of out-flow in the different kinds of rocks, 
and sustain the order:—porphyritic diabase, hornblende-andesite, 
pyroxene-andesite, later hornblende-andesite, pyroxene-andesite. 
The evidence given is partly lithological, and relates to rocks 
which have, as is implied, these perplexing transitions, so that it 
is set forth as probable rather than positive. The similarity in 
the rock of the two walls, claimed by Messrs. Hague and Iddings, 
is remarked upon adversely, but with the admission that the 
question is difficult to decide. 
Mr. Becker states that he found the diorite at the 3,000 foot 
level in the Comstock lode, identical with that at the top, and 
concludes that the crystallization does not vary with the depth; 
and the same for the diabase ; and in a belt at the surface about 
7,500 feet above the Sutro tunnel, he failed to find a serial pro- 
gress in degree of crystallization. Other points also are consid- 
ered, and in general his former positions are not yielde.. 
On the main -question, independent of Washoe, the difference 
between these observers appears to be small. For Mr. Becker 
says (p. 95) that “it has never appeared to me that a distinction 
between pre-Tertiary and Tertiary eruptions was a natural one,” 
but ‘an artificial substitute ;” yet he adds ‘“ which it would be un- 
wise to abandon until some available principle distinguishing little 
eroded from deeply eroded rocks is discovered and thoroughly estab- 
‘lished.” Allowing that the determination of the facts by direct 
observation should precede the attainment of the needed principle, 
and there would be agreement here also. The region is one of diffi- 
cult investigation on account of the natural transitions in the 
rocks, transitions also from the alteration of pyroxene to horn- 
blende, and the obscurity over the larger part of the exposed 
surfaces on account of the deep alteration and especially along 
the walls of the lode. Mr. Becker presents his arguments 
cautiously, making them probable rather than positive, and they 
indicate that he regards the question as still an open one. They 
appear to be insufficient, under the uncertainties, to set aside the 
improbability of his conclusions. 
Whatever uncertainty may exist with regard to the relations 
of the Washoe rocks, the principles deduced from them by Messrs. 
Hague and Iddings appear to be placed beyond reasonable dis- 
pute by later investigations in Great Britain and Italy. 
5. Volcanic Glass changed by heat alone to Pumice. In a 
paper on Marekanite, pearly glassy balls of volcanic origin (Geol. 
Mag., June, 1886), Professor J. W. Judd shows that the amount 
