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 300 or more feet. The time required 
for this accumulation of strata 
hurrying up the operation as much as we 
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 débris 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 
in their nature as is possible for any geological evidence to be. The whole 
* In addition to what has been already said of similar and perhaps even more extraordinary discoveries 
in Portugal. 
