i-knneman.] THE BOULDER, COLO., OIL FIELD. 329 
under an anticline, a syncline, or the limb of a fold. Oil might there- 
fore accumulate along certain lines, not because of being trapped in 
anticlinal arches, but because the products of the original decompo- 
sition or li distillation" (or whatever the process may be conceived to 
be) have been able to rise along certain lines and not along others. 
Whatever the explanation finally adopted, it is a noteworthy fact 
that the wells now pumping are, almost without exception, located on 
a nearly straight line, whose trend is north and south, parallel to the 
mountains. Should this line be found later to bear any relation to 
stratigraphic deformation, that relation will doubtless become an 
important element in future attempts to locate oil in this region. Such 
folds or faults, if determined at all, must be detected largely in accu- 
rately kept well records, because the rock disintegrates so readily as to 
make exposures of dips in surface outcrops of rare occurrence. There 
is no other way in which the same amount of work can yield results of 
such great financial importance as by the keeping of careful and 
minute daily records. 
The distribution of oil in belts parallel to the mountains can not be 
considered proved by the meager data thus far obtained ; and if proved, 
it might be due to causes not connected with structural deformation. A 
line parallel to the mountains was probably parallel to the shore line 
of the Cretaceous sea in which the sediments were laid down. The 
presence of oil might therefore be due to conditions of sedimentation 
at a nearly uniform distance from the shore, either the pl^sical char- 
acter of the sediments or the conditions favoring life. But these will 
not be discussed here. 
Shooting of wells. — All the wells pumped up to the close of the year 
1902 have been shot. The amount of nitroglycerin used in these 
shots has varied from 10 to 120 quarts. Dynamite charges have been 
as large as 500 pounds, 70 per cent nitroglycerin. The effects of these 
shots have not been uniformly favorable. The beneficial effects in a 
few of the best wells have doubtless been responsible for most of the 
later attempts. It is by no means certain as yet that this practice will 
be universal in this field. At least one well has recently begun pump- 
ing without being shot, and the owners have no immediate intention 
of shooting. The fact that the flow of some wells has decreased since 
the shooting will lead to greater caution, and it is to be hoped that 
it will lead to a more careful study of the conditions present in each 
well. 
The beneficial or harmful effects of a shot must depend largely upon 
the texture of the stratum yielding the oil, for it seems to be true that 
some shales are compacted rather than shattered by the explosion. 
For this reason, shooting is not practiced in the Florence field, which, 
of all the older oil districts, the Boulder field most resembles. Owing 
to the difference in texture of the various' beds yielding oil in the 
Boulder field, it is but reasonable to expect that the same shot which 
