i66 The American Geologist. September, 1902 
can. His notes arc a record of his daily collections, and, if a 
snccessfu-l geologist, of his daily imperfect inferences and de- 
ductions. But during the eight or nine months of office and 
laboratory work he has full opportunity for reflection. He is 
then likelv to see more of the common factors of the facts col- 
lected, and is more likely to see deeper into the underlying 
principles which explain them. This is still more true of the 
facts collected during previous years than in the current year. 
Indeed, in the field the observations of the current year are 
often too prominent on account of their recency, and it is only 
after some months have elapsed that they take their true pro- 
portion to observations of previous years. The use of the ma- 
terial collected not in one year only, but through mau}^ years, 
is necessarily in the office or in the laboratory , and it is only 
from such large masses of material that broad generalizations 
can be made. 
The inductions and deductions made in the office and the 
laboratory during the winter should be tested in the field in 
the following year in the light of the new ideas. The new ideas 
should not by a fraction modify the correctness of the observa- 
tions of the previous years ; they should be found as accurate 
as when made. But observations are always incomplete, and 
with a new idea one invariably adds valuable observations 
which were not noted before the idea was available. 
I once wrote to a number of geologists of this and other 
countries, asking the directions and dips of the dominant cleav- 
ages and joints for the various di.stricts and regions of the 
world with which they were familiar. From only a single ge- 
ologist did I obtain data of value. Some geologists wrote that 
they had not time to observe such subordinate phenomena! 
These men had evidently not learned the principle that the small 
but numerous agents or forces or structures may have as great 
or greater importance than more conspicuous but less common 
ones. Darwin should have taught every scientist the principle 
of the quantitative importance of the small factor when he 
showed hov/ great is the work of the apparently insignificant 
earth-worm. It seems to me that ioints are one of the impor- 
tant phenomena of geolog}- ; and this is true whether the point 
ojF view be deformation alone, physiography, metamorphism, 
circulation of groundwater, or tlie genesis of ores. 
