166 REPORT OF THE AMERICAN COMMITTEE. 
should not be taken as endorsing Hunt's views that all crystal- 
lines are ]>re-Paleozoic — as I know directly from examining the 
samples Hunt would call crystalline rocks, which are under the 
microscope plainly fragmental, having only a superinduced crys- 
talline structure, e.g., some mica-schists. These, I think, are 
undoubtedly often post-Archean. In other words, I think the 
truth lies between the hypotheses of geologists. ]\Iany semi- 
crystallines which by Hunt and his followers w^ould be looked 
on as Archean, largely perhaps because they are crystalline, are 
Post-Archean, or even Post-Paleozoic; nevertheless they diifer 
from the great Archean gneiss which is simulated not reproduced 
above the Archean. But, as I say, these are my notions only." 
Dr. S. F. Emmons says : " It is very probable that rocks may 
occur in the later formations which by themselves, or in hand 
specimens, would be indistinguishable from the crystalline rocks 
of the Archean." 
Prof. C. H. Hitchcock answers : " Yes ; because the Arch- 
ean 'conditions are repeated locally." 
Prof. N. H. Winchell does not know, but thinks that some 
of the later crystalline rocks have been confounded by geologists 
with rocks of the Archean age. They may, however, be distin- 
guishable when carefully studied. 
Prof. M. E. Wadsworth answers : " Yes." 
Prof. B. K. Emerson answers : " Yes." 
Capt. C. E. Dutton replies : ^' The answer to this question 
should, it seems to me, depend somewhat upon what constitutes 
a distinction. If we draw distinctions fine enough we can dis- 
tinguish petrographically two fragments of the same boulder. I 
know of Paleozoic rocks which I think ought to be called 
schists, and which have a great deal in common with Archean 
rocks; but if anybody is determined to find a distinction, he can 
easily do so. Broadly speaking, however, all the Archean rocks 
I have met with have a character of their own, and, however 
nearly they may be approached by later formations, distinctions 
can easily be made." 
Prof. Pumpelly : " There are crystalline rocks in the Paleo- 
zoic which have a strongly marked Archean habitus; but I 
think there are some Laurentian rocks of which the character- 
istics are not repeated in later times." 
Prof. A. Winchell : " Yes." 
