118 NEW YORK STATE MUSEUM 
introduced as an induration effect or was traded in a process of 
replacement for parts of the rock that have disappeared: How 
shall one designate these conditions? 
13 A belief in recrystallization has come to stay. Recrystalliza- 
tion does not presuppose any particular composition or particular 
structure. Shall we call the group of such products the recrystalli- 
zationites? ! ve 
Fundamentally there are two divisions of this group — the mas- 
sive ones and the foliated or stretched ones; but we have no clearly 
recognized names for them. 
If I call the latter foliates, as Miller does in his reclassification of 
metamorphic terms, in what way shall we distinguish the ee 
foliated rocks of both igneous and sedimentary origin? : 
There is, of course, no object in pressing these questions sie 
They have been used only to indicate at how many points the termi- 
nology and classification schemes of petrography fall short of the 
working conceptions of the applied geologist. If it is true, as it 
seems to me, that the rightful field of petrology is rock interpreta- 
tion, and that its greatest service lies in its contribution to geologic 
history, then, sooner or later, a considerable modification in termi- 
nology is sure to come in petrography itself. 
Petrologists of the new school will have to be, first of all, geolo- 
gists both in fundamental training and in thinking habit, rather than 
mineralogists, because their subject is an intimate part of the field 
of geologic history, and their science is but a branch of ' ne pee 
science of geology. | 
- Petrogenesis, the life history of rocks — geologic eee hid. m 
the obscure inner recesses of the rocks themselves — these ove the 
chief interests of the new petrology and these CMe Si map out 
its ane service. 
