Wadsworth.] 
244 
[October 19, 
2. The present writer’s statements of what the rocks are in the 
collection under discussion do not aoree with Mr. Merrill’s defini- 
o 
tions of diorite, diabase, hornblende porphyry, gabbro, basalt, 
andesite, etc. ; and therefore the same conclusion is to follow as in 
the preceding. 
To the first it is simply to be said that the word original was 
used in direct opposition to the terms alteration and denitrifica- 
tion in the same sentence, and had no reference to the “ original 
use ” of the term micro-felsitic. The word original meant in the 
sentence, that which was believed to be the direct product of the 
cooling magma, in contradistinction to that which was the pro- 
duct of subsequent changes in the rock. The truth of my previous 
statement is virtually admitted by Mr. Merrill ; who, however, fell 
into the error of not regarding it as the point at issue. 
Concerning the second point, it is to be said that the usual 
classifications had been rejected by me and the principles of 
another briefly sketched. Further, it was pointed out where, in 
this classification, certain of the specimens described in Yol. YI, 
of the Fortieth Parallel reports, would be placed by me. 1 
Now it was not intended that these specimens should be made 
to conform to any of the artificial classifications that were rejected, 
but which Mr. Merrill has adopted from his teacher — Zirkel. 
In both of these counts, which covet’ all of importance in Mr. 
Merrill’s paper, he has totally failed, <ua account of erroneous 
views regarding my statements and oJPnions. These errors of 
Mr. Merrill were unnecessary, since he could have easily ascer- 
tained my meaning upon any points not clear to him, either in 
person or through mutual friends. 
Furthermore, it would seem that sufficient attention had been 
called in my previous abstract to the three distinct classes of 
materials found in rocks, to prevent the first mistake. Surely in 
the second case it was unnecessary, since it is in violence of the 
canons of criticism, to demand that an author’s statements shall 
agree with that which he has especially rejected. This, Mr. Mer- 
rill evidently knew, since he has adroitly endeavored to turn my 
• 
own principles against me when he thought he could do so. 
i It may be remarked that the originator of a classification may possibly know 
whei’e specimens are to be placed according to the principles of that classification as 
well as any one else. 
