130 BULLETIN UNITED STATES GEOLOGICAL SURVEY. f VolV. 
basaltic fragments, many of which are of great size ; there is, however, 
always enough tulaceous and other fine-grained material to fill in the 
interstices and act as a cement. These beds are massive and irregular, 
and seem to have accumulated too fast to be thoroughly redistributed 
by the waters. Only the stronger trees of the forest seem to have with- 
stood the fierce storms of rocks that must have prevailed at the period of 
their entombment, as the smaller trunks and branches are prostrate or 
totally destroyed. In most cases where upright trunks penetrate the 
entire thickness of an enclosing bed, the tops may be seen to terminate 
with the upper surface of that bed, as if causes had acted at the begin- 
ning of the deposition of the succeeding stratum to plane down the 
irregularities of the old surface. In due course of time, this succeeding 
stratum produced its growth of forest, which followed its many prede- 
cessors into the subterranean depths, and in its turn was buried by the 
rapidly accumulating conglomerates. This remarkable alternation of 
events seems, in a general way, to have been kept up from the beginning 
to the end of the period. 
The very precipitous character of the cliffs prevented me from reach- 
ing the upper part of the wall at this point, but I succeeded in making 
my way to the summit of the mountain at two other points, and found 
that everywhere the section was practically the same. 
O 11 the opposite side of the valley the same conditions were observed : 
the fossil trees occur at the highest point reached, 3,000 feet above the 
river. The ranges that form the rim of this valley on the north and east 
reach an elevation of 11,500 feet, and as the conglomerates may be seen 
reaching and forming the loftiest summits without perceptible break or 
change of character, it is probable that they will be found to enclose the 
remains of forests throughout. 
On some of the higher summits to the east of Yellowstone Lake, simi- 
lar stratified conglomerates contain silicified wood in a very fragmentary 
state. These conglomerates are composed mainly of basaltic and tra- 
cliytic materials, but contain large quantities of fragments of sand- 
stones and quartzites, which leads to the conclusion that portions of the 
earlier Tertiary strata have been broken up and ejected with the igneous 
products. It is quite probable that these strata were among the later 
products of the Volcanic Tertiary age proper. They are generally found 
abutting against masses of unstratified igneous materials that probably 
mark the sites of islands which were doubtless volcanic centers. I find 
that as we recede from these centers of eruption the strata diminish very 
perceptibly in thickness and coarseness of materials, and have at the 
same time a very x>erceptible dip toward the surrounding valleys. One 
is at times led to suspect that portions, at least, of these beds are of sub- 
aerial formation, as is the case with extensive strata about the cones of 
modern volcanoes, but there are a multitude of facts that go to prove 
that the greater part of the formations of this age were rearranged or 
sedimented in water. 
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