Training of a Geologist. — Van Hise. 167 
While the work of each geologist should be based upbn 
thorough field and office work, and thus have an inductive bas- 
is, one 'Should not there stop, but should by deduction ever be 
looking forward. No one ever held more firmly to fact as a 
basis for induction than Darwin, but also, no man has more 
successfully projected by deduction beyond his facts than Dar- 
win. This in biology was a task- of extraordinary difficulty. 
In geology one who has a firm grasp of the principles of phvs- 
ics and chemistry may be more daring. Their principles, if 
not more definite than the laws of biology, are at least better 
known and more simple. Therefore, one, after having ob- 
served the facts in a district and grasped the principles which 
explain them, may deduce what are likely to be the facts in the 
field and their relations in advance of observation. Or more 
colicretely, after one gets the correct idea as to the meaning of 
the phenomena for a certain district, he often can tell in ad- 
vance of observation what he will see, — or can find what I call 
'geology made to order.' 
There is no better or more severe test of a theory than one's 
capacity to find geology made to order. If observation of an 
area shows facts are not as expected, this is certain evi- 
dence that one or more factors in the problem have been omit- 
ted and that the theory is inadequate. In so far as the theory 
is adequate, the geology will be found as anticipated. The rea- 
son for this is the very great complexity and delicate adjust- 
ment of the phenomena of nature. To illustrate, if the manv 
parts of some complex machine, such as a great printing press, 
or a chronometer, were scattered far and wide, and then one 
should gather many of these parts, and try to fit them, he might 
find that certain numerous parts fit perfectly. If this were so. he 
would know to a certainty that these parts are in the correct po- 
sitions and relations, even if he did not know the relations of 
these parts to other parts or the purpose of the whole; for so 
complex and exact is the adjustment that there is but one way 
to put the parts together. Another set of parts might be found 
and these made to fit. But doubtless certain parts would not be 
found. These would be missing links necessary to make a per- 
fect machine. In this situation, if the man had a genius for me- 
chanical construction and an insight into principles, he might 
be able to understand the purpose of the whole, and finally to 
