108 NEW YORK STATE MUSEUM 
to distinguish and recognize words is a first step toward reading. 
There is, to my best belief, no such thing as a rational science of 
petrology wholly apart from the great science of geology. What- 
ever of significance attaches to a rock is largely gathered to it from 
the processes and agents and forces and conditions of its own geo- 
logic setting and history. Practically all of petrology’s own con- 
tribution, if these meanings can be read, returns to geology again to 
enrich the knowledge of that great field —the field of geologic 
history. 
In so far as a nice discrimination and a true sense of proportion 
serve in detecting evidence of former conditions or processes or 
changes or sources, they contribute directly to the new aim. It is, 
of course, appreciated that methods of discrimination and classifica- 
tion may have immense disciplinary and training value in education 
quite apart from the chief aim of a science itself; but then it should 
be frankly recognized as an educational objective. For the science 
itself, discrimination for discriminative sake alone is not enough. 
Meaning or history are higher aims. Interpretation is the objec- 
tive of the new school in petrology, just as it is in the general science 
of geology. 
The reading of the life listory of a rock 1s a much higher accom- 
plishment than to classify or describe. It 1s the mam objectwe of 
the new petrology. 
The steps in determination of the origin and successive modifica- 
tions of an ore are as proper a petrographic study as is the life his- 
tory of an igneous rock or a sediment. 
Whether or not a rock has been much modified since its original 
deposition, whether or not some of its present makeup has been 
added to it since that time, and whether or not it records some pecu- 
liar reversal in the course of development along which it first started, 
may be of immensely more importance than its name or its mineral 
proportions or any amount of minute description, or even a com- 
plete chemical analysis with all sorts of formal recasts of its 
elements. 
Practical work covering many years and touching a very wide 
range of materials and problems has convinced the writer that the 
new aim is practicable and that the greatest usefulness of petrology 
is in some way involved in unraveling the origin and life history of 
rocks. The principal field of this kind of petrology lies in the read- 
ing of obscure history. Its chief claim to distinction lies in the 
