PNDIVMI DUES OFeSELRATIGRAPTHIIC CLASSIFICATION: 
DISCUSSION: 
THE exceedingly suggestive paper appearing in a recent 
number of the JouRNAL,* under the above title, brings up for 
discussion some of the very practical problems which confront 
the geologist in his daily work. Their importance will perhaps 
warrant a supplementary discussion of the subject from the 
point of view of the mining geologist; not that this is necessarily 
the most important point of view, but rather that geologists in 
their devotion to the interests of pure science are apt to over- 
look the needs of fellow workers in applied science. The debt 
of science, as expressed in the generous appropriations of the 
various states and the general government for geological surveys 
and similar institutions, is too great to warrant us in failing at 
any time to give the highest possible return in practical results. 
While the great purpose of geologic science, to reconstruct the 
past history of the earth, must be kept steadily in view, it is 
well, if we would have the means to carry on that work, that we 
should keep no less steadily in view the wants of the plain 
citizens who are developing our country’s resources. 
The paper in question is particularly welcome to the mining 
geologist because it emphasizes the importance of mapping many 
of those features which will help him most in directing the 
development of mines and mineral deposits. One engaged in 
such work needs somewhat more complete data in regard to the 
lithology of the rocks and the geographical distribution of the 
more minute rock units than are necessary for ordinary geologi- 
cal research. He needs also a very minute knowledge of local 
structure and as perfect a knowledge as may be of the processes 
of change through which the rocks have passed. 
In studying the genesis of any ore deposit it is needful, first, 
‘BAILEY WILLIS, /zdividuals of Stratigraphic Classification, JoUR. GEOL., Vol. 
IX, No. 7, October-November, 1901, pp. 557-69. 
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