444 TROPICAL NATURE 



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 Beds 

 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 



