354 
DEMESNE OF PETROLOGY 
tience with which are received the rock names based upon com¬ 
positional differences. The chief positive influence comes from 
the practical use made of petrologic methods by the various work¬ 
ers in Applied Geology, rather than from the transcendent results 
of scientist pure and simple. 
In the past our leading petrographers lent the weight of their 
influence and the fruits of their labors to field of tabulated de¬ 
tails and of the niceties of systematic arrangement, as if the chief 
aim were to divide and subdivide and divide again, and to discover 
still more subtle and intricate methods or bases for further subdi¬ 
vision. Formal description was recognized as a more or less nec¬ 
essary accomplishment, but this commonly dealt with the features 
useful in the scheme of classification being followed, or else it 
relaxed into a rambling account of everything in sight. 
Thus, ready ability to describe and to classify rocks especially 
marked an accomplished petrographer. To discover in a rock 
some slightly different mineralogic proportion and to be thought¬ 
ful enough to give such rock a new name established one as an 
active and original contributor to the science. Some of the 
methods made use of have even gone so far as to completely 
destroy the actual rock before beginning the task of fitting it into 
its proper niche in the accepted classification. Sometimes there 
were established by this method constituent factors that the live 
rock never had, while there was overlooked or neglected other 
much more important features which it did have. 
In stating these facts one does not desire to be understood as 
attempting to belittle this or any other pioneer work. It is simply 
for the purpose of laying foundations for a revised prospect by 
emphasizing the severe limitations of current practice in some 
places. 
Much as one must appreciate and value the genuine contribu¬ 
tions which have been made by the systematic petrographer, and 
by the chemical petrographer, through the nice points of discrimin¬ 
ation and the increased appreciation of sound chemistry and the 
rigid requirements of quantitative thinking, and much as one must 
also continue to use the same methods of discrimination, the con¬ 
viction is overpowering that the apparent object in view is not a 
sufficiently high goal. This is not the chief or most promising 
field of rock study. 
