

LENGTH OF TIME SINCE MAN'S APPEARANCE, 



285 



phases of volcanic activity and of aqueous invasion, during which the alter- 

 nations of gravel, sandstone, and volcanic materials were piled upon each 



■ 



other to the height of from 200 to 800 or more feet. The time required 

 for this accumulation of strata — hurrying up the operation as much as Ave 

 possibly can — will have been considerable. Some of the finer deposits of 

 clayey materials are of great thickness, and must have occupied a long 

 period in their deposition. Even the more turbulent torrents bearing down 

 the coarser gravels from the more elevated regions must have persisted dur- 

 ing long periods of time, in order so effectually to spread the debris they 

 conveyed over such an extensive area. Neither is the transition from a 

 period of volcanic activity to one of repose likely to have been always abrupt. 

 The analogy of present volcanic action shows clearly enough that consider- 

 able time is required for thick accumulations of erupted materials of various 



texture and composition to be formed. 



But if time is needed for the accumulation of the strata in question, how 

 much more is imperatively demanded for the accomplishment of the im- 

 mense denudation and erosion which the region has undergone, and of 

 which some idea has been given in describing the phenomena of Table 

 Mountain ! And the farther north we go, the more extensive this erosion 

 proves to have been. 



The discoveries in California, even admitting all that seems to be indi- 

 cated by the truly wonderful occurrences of human remains and works of 

 art under Table Mountain, are by no means unprecedented or unsupported 

 by similar testimony from other countries. Almost every month brings us 

 from some part of the world proofs of man's having existed at a remote 

 epoch, and for an indefinite period, in what we may call his primitive condi- 

 tion, that is to say, in the lowest stage of development in which he could 

 continue to exist as man. It is only necessary to mention in this connec- 

 tion * the discovery of stone implements by the officers of the Geological 

 Survey of India, scattered over a considerable portion of the Indian Penin- 

 sula, and occurring under circumstances which prove very clearly that great 

 changes have taken place in the physical geography of that country, since the 

 people lived by whom these implements were fashioned. The evidences to 

 this effect have been accumulating for many years, and are as unmistakable 

 *n their nature as is possible for any geological evidence to be. The whole 



* In addition to what lias been already said of similar and perhaps even more extraordinary discoveries 

 fc Portugal. 





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