300 



MAN AND THE GLACIAL PERIOD. 



Counties, California, reveals a state of things closely re- 

 sembling, in important respects, that in western Idaho. 

 At first sight the impression is made that an immense 

 lapse of time must have occurred since the volcanic erup- 

 tion which furnished the lava of Table Mountain. The 

 Stanislaus River flows in a channel of erosion a thousand 

 feet or more lower than the ancient channel filled by lava, 

 and in two or three places cuts directly across it. An 

 immense amount of time, also, would seem to be required 

 to permit the smaller local streams to have worn away so 



Fig. 98.— Section along the line, north and south : r' r', old river-beds ; r r, 

 present river-beds ; L, lava ; si, slate. 



much of the sides of the ancient valley as to allow the 

 lava deposit now so continuously to rise above the general 

 surface. Still, the question of absolute time cannot be 

 considered separately without much further study. It is 

 by no means certain that, when the lava -stream poured 

 down the mountain, it always followed the lowest depres- 

 sions ; but at certain points it may have been dammed 

 up in its course by its own accumulations so as to be turned 

 off into what was then an ancient abandoned channel. 



The forms of animal and vegetable life with which 

 the remains of man under Table Mountain are associated, 

 are, indeed, to a considerable extent, species now extinct 

 in California, and some of them no longer exist anywhere 

 in the world. But a suggestion of Professor Prestwich, 

 in England, made with reference to the extinct forms of 

 life associated with human remains in the glacial deposits 

 in Europe, is revived by Mr. Becker, of the Geological 

 Survey, with reference to the California discoveries ; his 



