STONE AGES OF CEYLON. 101 
will cling to the tip of the tongue more readily than will the 
broken stem of a new clay pipe. 
The mottled cherts often display differential weathering, 
the mottling, by reason of its,more resistant nature, standing 
out in bold relief from the remainder of the stone. 
I am strongly disposed to believe that exposure to the 
weather is an essential factor in patination. I do not wish to 
be dogmatic on a subject which we have no time to pursue ; 
but I may add that I am inclined to think that patination 
never comes about without exposure. At any rate, I am 
convinced that no one who studies Ceylon stone artefacts 
impartially will place much reliance on degrees of similar 
patination as indices of age. That an artefact must be old 
to be patinated I have no doubt, but I do not think it follows 
that an old artefact must of necessity be patinated. 
V.—THE GEOLOGY OF THE PLATEAU DEPOSITS AND 
THEIR DERIVATIVES. 
In order to understand the history of early man in this 
country, it is necessary to pay some attention to the deposits 
in which such relics as he has left may yet be found. I have 
already briefly outlined these beds, and would not dwell 
further upon them were it not that the story they tell is one 
full of interest and significance. 
The oldest accumulations with which we shall deal in this 
connection are what I have called the plateau deposits for 
reasons which will be presently apparent. 
They are very widely distributed, and were, no doubt, at one 
time developed along the entire seaboard of the Island and 
covered much of the lowland regions. Since then, however, 
they have suffered denudation, and are now represented by 
detached and often widely separated outcrops. 
The plateau deposits are generally venetian or brick-red 
in colour. They are liable, however, to be bleached from 
various causes, the growth of vegetation being one, when they 
present various shades of buff; while some detrital beds 
derived directly from them are snow-white. 
They consist typically of two strata; the lower of these, 
though varying a good deal in composition in different areas, 
4 6(8)19 
