STONE AGES OF CEYLON. 93 
states it thus: “‘In all cases where identical types of imple- 
ments from above and below the surface can be compared, 
there is no question that the former is on the average consider- 
ably larger than the latter. The only marked exception is 
the large round scraper from the pigmy-layer alluded to. I 
have also picked up on the surface of Bungalow Hill a single 
arrowhead ; it is significant that this differs, not only in size, 
but in type from any recovered from below ground. I do not 
attempt at present to draw any hard and fast conclusion ; but 
the evidence before me inclines me now to believe that the 
two types are separated in time.’’* This may be so, of course, 
but it is well to remember that in soils subject to conditions 
such as those which affect the patanas, the larger pebbles and 
rock-fragments are situated at the tops, when they themselves 
are both chemically and physically stable, and are not derived. 
from the strata underneath. 
Microscopic examination shows that the soil-cap on the hill 
referred to is due to the weathering of the rocks below. The 
chip-layer is situated, at a depth seldom less than two inches 
or more than six beneath the surface ; since, as can be shown, 
the soil-cap was not deposited over the chip-layer from an 
extraneous source, it follows that the chips must have sunk, 
as there can be no doubt that they were originally on the 
surface. 
Worms, as far as my observations go, are decidedly rare on 
the patanas, so their participation as burying agents may be 
safely ignored ; burrowing insects, however, are more common. 
The latter carry out most of their work during the dry season, 
when a large percentage of the soil which they bring to the 
surface must be blown down the hill slopes. Consequently 
the chips descend chiefly by a process of undermining, and 
since small chips are more easily undermined than large ones, 
the tendency is for the larger fragments to lag behind in the 
downward movement. Moreover, large stones protruding 
from the soil are more easily dislodged from their positions by 
accidental circumstances, and are also less liable to be pressed 
into the soil by the feet of animalsand men who may by chance 
trample on them. 

* Loc. cit., p. 66. 
3 6(8) 19 
