386 
posed of volcanic or metamorphic rocks. The spaces between 
them are level desert surfaces. Towards the north and west, on 
the tributaries of the Columbia, Klamath, or Pit Rivers, the 
plateau is cut by these streams, and the deposit can be examined. 
The rocks are nearly horizontal, some are coarse volcanic ash, 
with fragments of pumice and scoriz. Others denominated 
**concrete” resemble the old Roman cement. Many are quite 
white, and are generally known as ‘‘chalk-beds,” though they 
contain no lime. The late Prof. J. W. Bailey determined these 
to consist of the remains of fresh-water species of Diatomacez. 
The stratification and horizontality of these beds show them 
to have been thrown down from great bodies of water 
which once covered the greater part of these level plains. 
From south-western Idaho and eastern Oregon have lately 
been brought large collections of animal and vegetable fossils, 
of great variety and interest. The plants were mostly col- 
lzcted by the Rev. Thomas Congdon, of the Dalles, Oregon, at 
great risk of life and while exposed to great hardships, on the 
flanks of the Blue Mountains, They are apparently Miocene, 
forming twenty or thirty species, nearly all new, and which re- 
present a forest growth as varied and luxurious as can be found 
on any portion of the continent. The animal remains came mostly 
from the banks of Castle Creek in the Owyhee district, Idaho. 
These were sent by Mr. J. W. Adams of Ruby City. They con- 
sist of bones of the mastodon, rhinoceros, horse, elk, and other 
large mammals of which the species are probably in some cases 
new, in others identical with those obtained from the deposits 
examined by Dr. Hayden. There are also bones of birds and 
great numbers of the bones and teeth of fish. These last are cy- 
prinoids applied to Mjlopharodon, Milocheilus, &c., some three 
feet and more inlength. Also many fresh-water shells, as Uzio, 
Corbicula, Melania, and Planorbis. ‘Theseillustrate the inhabitants 
of the extinct lakes, which were of a much larger size and greater 
depth than the great fresh-water lakes which now lie upon our 
northern frontier. Between these were areas covered with 
a luxuriant and beautiful vegetation and inhabited by herds of 
elephants and other great mammals. In the streams were numbers 
of fish and mollusks of species now extinct. Gradually these 
lakes evaporated and at last became dry. In the Klamath lakes 
and Suisun Bay we have their remanents, whilst on the Columbia 
the drainage streams have cut camons two thousand feet deep. 
At times the peace and quiet of this country were disturbed by 
violent volcanic eruptions from the peaks of the Sierra Nevada, 
which ejected showers of ashes covering the land and filling the 
lakes, as is seen in the strata now existing, some ten and twenty 
feet thick. Sometimes lava was thrown out and covered hun- 
dreds of miles of surface, and is now seen as solid basalt. Then 
quiet reigned, and new fresh-water deposits were formed, only 
to be succeeded by other volcanic disturbances. Some parts of 
this plateau have not been drained, and the remains of the 
ancient lakes now exist as Salt Lake, Pyramid Lake, and others. 
These are gradually diminishing, as is to be seen by indica- 
tions all around their borders, where we can trace ancient 
shore lines. The alkali plains and salt flats mark the places of 
dried-up lakes ; all of these still existing being excessively salt. 
This is the state of things at the north. In the south, the great 
Colorado plateau is without mountain barriers or local basins, 
and ther2 are few traces of extinct lakes. This arid district was 
once a beautiful and fertile plain, drained by the Colorado, whi:h, 
on the western margin poured over a precipice five thousand feet 
or more high, into the Gulf of California, which then reached 
several thousand miles farther north than it does now. In time 
the river cut its way farther back through the subjacent rocks, and 
at last formed that remarkable gorge, nearly a thousand miles 
long and three to six thousand feet deep. As the channel 
deepened, the country around became dryer, until it was the arid 
plain we find it now. Almost no rain falls on this plain, there- 
fore the walls of the cazoz remain sharp-cut precipices unaffected 
by moisture. On the east of the Rocky Mountains is the great 
plateau country of the plains, which differs from the country to 
the west, by not being bordered on its east by a mountain chain, 
but sloping gradually to the Mississippi. Its surface was also 
covered by great fresh water lakes, larger, if not more numerous, 
than those now existing on our northern boundary. From the 
northern portion of this plateau Dr. Hayden has brought his 
specimens, and he has there obtained a harvest of scientific 
truth which will form for him an enduring and enviable 
monument. He has studied the deposits which accumulated 
in these lakes, and they are very rich in specimens of both 
animal and vegetable life. The vertebrate remains have 
been studied by Dr. Leidy, who has published his investiga- 
NATURE 
- [ Sept. 8, 1870 
tions in the splendid monograph so well known, and which 
forms a contribution to palzontology, not second in value or 
interest to that made by Cuvier, by his illustrations of the fossils 
from the Paris basin, nor to that of Falconer and Courtly, 
descriptive of the Sewalik hills of India. The first instal- 
ment of the plants have been described by Dr. Newberry, 
in the report of Colonel W. F. Reynolds, U.S.A., not 
yet published. | The descriptions are published in the 
Annals of the Lyceum of Natural History of New York, 
vol. 9, 1868, The general conclusions from these examinations 
have greatly enlarged the flora of the Tertiary and Cretaceous 
periods. Since then largely additional material has been collected 
by Dr. Hayden, Mr. Congdon and Dr. Le Comte, and Dr. New- 
berry ; and in Alaska by Mr. W. H. Dall and Captain Howard, 
and by others in Greenland. The flora and fauna of the lake 
deposits on both sides of the Rocky Mountains apparently 
belong to one and the same geological age, and tell the same 
story as to topography, climatic conditions, and development of | 
animal and vegetable life. There is a striking difference in one 
particular between the deposits east and west. In Oregon, 
Idaho, and Nevada, volcanic material has accumulated in the. 
lake basins to a much greater extent than on the east of the 
mountains. The deposits of the Upper Missouri regions are 
shales, marls, and earthy limestones, with immense quantities 
of lignite and almost no traces of volcanic material, The 
animals and vegetables of the Tertiary here were in much 
greater number thannow. This existed long enough for thou- 
sands of feet to accumulate in the lake basins, and sometimes 
these deposits are found turned up on edge on the flanks of the 
mountains, showing that this chain, although existing in embryo 
from the earliest palcozoic ages, has been subjected to great 
modifications. The collections made by Dr. Hayden at various 
points differ among themselves. In every bed are new species, 
and between some deposits there are no connecting links. In 
the beginning of the cretaceous the land surface and climate of 
this continent were similar to the present period, the trees for the 
most part belonged to the same genera. Then most of the region 
west of the Mississippi sunk beneath the ocean, and the cretaceous 
deposits were made containing more tropical species. There were 
islands in the western sea, and the Gulf Stream had a course 
north and west from the Gulf of Mexice to the Arctic Sea. In 
the earlier Tertiary ages the continent here emerged from the 
ocean and approached the previous and present conditions 
indicated by the flora. In this category are to be placed the Green 
River Tertiary beds, those of Mississippi studied by Lesquereux, 
and those of Brandon, Vermont. Inthe Miocene the continental 
surface was broader, the western lakes were fresh, and the vege- 
tation very much like that of the present day. A few palms then 
grew as far north as the Yellow Stone River, and a flora flourished 
in Alaska and Greenland as varied and as luxuriant as now grows 
along the fortieth parallel. At this time land connected Europe, 
this continent, and China, as the flora in this region was essen- 
tially the same, a large number of plants being common to the 
three continents. The mammals were peculiar; over our 
western plains rolled herds of great quadrupeds rivalling in 
number and variety those of southern Africa at the present time. 
This state of things continued during the Pliocene age and up 
to the ice period. In the middle Tertiary the climates of Alaska 
and Greenland were those of New York and St. Louis at present. 
Then came the Glacial epoch, and the climate of Greenland of 
the present time is brought down to New York, and all the north- 
ern portion of the continent is wrapped inice. This change of 
climate was gradual, but the animals and vegetables were driven 
southward until the glaciers reached the thirty-eighth or fortieth 
parallel, when a temperate climate prevailed in Mexico, and only 
on the southern border would the temperature be what it had 
previously been on our northern border. Thus nearly all the 
animals were exterminated or forced into very narrow limits in 
southern Mexico. Plants bore their expatriation better, andas a ~ 
consequence we find the present flora of our continent much 
more like that of the Miocene than is our fauna, though most of 
the forest-trees have become extinct. Of these the Glyptostrobus 
is an example, which grew all over our continent and northern 
Europe. Ia the glacial period it was exterminated except in 
China, where it now grows. So when we compare the present 
flora of China and Japan with that of the eastern half of our 
continent, we find the strongest proofs of their relation-hip ; many 
species are identical, while others are but slightly changed. Some 
of the great mammals of the pre-glacial period bade defiance to 
these changes, as the mastodon and elephant, bothzof which 
could endure great changes of climate, and the mammoth, we 
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