444 
TROPICAL NATURE 
VIII 
surrounding plain or valley. What was once a single lava 
stream now forms several detached hills, the tops of which 
can be seen to form parts of one gently inclined plane, the 
surface of the original lava flow, now 1000 feet or more 
above the adjacent valleys. The American and Yuba valleys 
have been lowered from 800 to 1500 feet, while the Stanis- 
laus river gorge has cut through one of these basalt-covered 
hills to the depth of 1500 feet. 
While travelling by stage, in the summer of 1887, from 
Stockton to the Yosemite valley, I passed through this very 
district, and was greatly impressed by the indications of 
vast change in the surface of the country since the streams of 
lava flowed down the valleys. In the Stanislaus valley the 
numerous “ table mountains ” were very picturesque, often 
running out into castellated headlands or exhibiting long 
ranges of rugged black cliffs. At one spot the road passed 
through the ancient river-bed, clearly marked by its gravel, 
pebbles, and sand, but now about three or four hundred feet 
above the present river. We also often saw rock surfaces of 
metamorphic slates far above the present river-bed, thus 
proving that the original bed-rocks of the valley, as well as the 
lava and gravels, have been cut away to a considerable depth 
since the epoch of the lava flows. The ranges of “table 
mountains,” now separated by deep valleys more than 1000 
feet below them, could easily be seen, by their perfect agree- 
ment of slope and level, to have once formed part of an 
enormous lava stream spread over a continuous surface of 
gravel and rock. 
Fossil Remains under the Ancient Lava Reds 
These great changes in the physical conditions and in the 
surface features of the country alone imply a great lapse of 
time, but they are enforced and rendered even more apparent 
by the proofs of change in the flora and fauna afforded by the 
fossils, which occur in some abundance both in the gravels and 
volcanic clays. The animal remains found beneath the basaltic 
cap are very numerous, and are all of extinct species. They 
belong to the genera rhinoceros, elotherium, felis, canis, bos, 
tapirus, hipparion, equus, elephas, mastodon, and auchenia, and 
form an assemblage entirely distinct from those that now 
