= 
JANUARY 25, 1884. ] 
From the deeply eroded valley of the Yellow- 
stone, almost all the facts as to the pre-tertiary 
history of the park are drawn; and the line of 
this river appears to have been determined by 
a great fault for which a minimum estimate of 
the displacement is given at 15,000 feet. This 
fault was probably synchronous with the general 
Rocky Mountain uplift, and is presumed to be 
in more or less direct causal connection with 
the subsequent remarkable history of the dis- 
trict. It is not a simple fissure, but a break 
along which the edges of the strata have been 
much dragged and contorted, particularly on 
the dropped side; appearing, in fact, to have 
the character of a great flexure pushed to 
fracture. On its northern side rises the Yel- 
lowstone Range; while to the south, in the 
depressed area, are found the evidences of 
that prodigious volcanic activity of which the 
actual thermal phenomena are the last linger- 
ing stages. 
From the older tertiary rocks of the park 
have been collected a number of plants which 
Professor Lesquereux refers to the Fort Union 
group ; but, before the inauguration of the vol- 
canic periods, these beds, together with the 
paleozoic rocks, 
had been deeply 
SCIENCE. 
105 
of Amethyst Mountain, plants of upper mio- 
cene or lower pliocene age have been identified. 
Very much yet remains, however, to be dis- 
covered in the history of this prolonged period, 
which, in its succession of volcanic outbursts 
alternating with epochs of quiet river-work, 
much resembles that of the classic tertiary vol- 
canic region of central France, and may, when 
fully disclosed, tell as interesting a story. In 
Amethyst Mountain some of the latest stages 
are well exemplified, and we have, perhaps, the 
finest series of buried erect forests ever dis- 
covered. The volcanic rocks, here character- 
istically conglomeritic, show a thickness of five 
thousand feet, and are charged almost through- 
out with the silicified remains of ancient for- 
ests. The lower layers are comparatively fine 
grained, but are followed by conglomerates 
which become coarser and more breccia-like 
in ascending, but are throughout interbedded 
with sandstones, and shaly layers largely tufa- 
ceous in character, and appear to be partly 
water-bedded and partly sub-aerial. The in- 
tervals between successive eruptions have been 
sufficient to allow the surface to become clothed 
again and again by a heavy forest-growth, each 
of which has been 
destroyed and bur- 
scored by erosion. 
ied in turn. 
There can be lit- 
The earlier flows 
tle doubt that the 
of trachyte and 
rhyolite poured in- 
hot- springs have 
to the then exist- 
been continuously 
ing valleys till they 
in existence since 
were, in many 
cases at least, en- 
the volcanic peri- 
od ; and actual evi- 
tirely obliterated, 
dence of their great 
and the successors 
antiquity is found 
of these first rivers 
forced to cut new 
channels having 
in the occurrence 
of fragments of the 
characteristic cal- 
little or no refer- 
ence to the posi- 
tion of the old. 
Subsequent lava- 
flows again filled 
these later valleys, 
and, through the 
succeeding basal- 
tic and conglom- 
eritic epochs of 
careous deposit in 
some of the high- 
er river-terraces, 
since the forma- 
tion of which the 
Yellowstone has 
cut for itself a 
canon a thousand 
feet in depth. 
For an account 
activity, this pro- 
cess appears to 
have been repeated 
many times. The entire period of volcanic ac- 
tivity must have been of extremely long dura- 
tion, and may have lasted through a great part of 
the tertiary. From the volcanic conglomerates 
GRAND CANON OF THE YELLOWSTONE. 
of the hot-springs 
and geysers as 
found at the pres- 
ent day, we must, however, turn to the second 
section of the report, in which Dr. Peale treats 
the subject in an exhaustive manner, tabulat- 
ing over two thousand springs and seventy-one 
