270 SPOLIA ZEYLANICA. 
but some curious hydrographical phenomena, the facts of 
subterranean erosion, the rapid denudation of the coast, and 
the abrupt ending of shallow platforms under the sea suggest 
that the land is being slowly submerged. If such is the case, 
and if depression continues for a sufficiently lengthy period, 
fresh sediment will be distributed over the coastal belt ; fresh 
kadu-suli may be deposited upon the flats, and the bones 
and teeth of animals lying on the ground will be covered by 
deposits similar to those on which they rest. So will these 
accumulations grow till a change of conditions (the result of 
depth attained or some other circumstance) necessitates a 
change of material precipitated. Thus, a bed of clay may be 
covered by a layer of sand, or coral reef submerged in mud. 
In the light of these considerations we may interpret the 
exposures of the Wellawatta trench, but before doing so it 
will be as well to consider the section in general (Plate IT.). 
The points A, B, C, and D vary considerably in relative 
position along the coast. A is the modern shore line, B is 
the edge of the coastal plane, C is the edge of an ancient beach, 
and D is the junction of the coastal plane with the Archean 
crystalline rocks which form the main mass of the Island. 
In places where coastal erosion is rapid (southern part of 
the Western Province and Southern Province) A, may coincide 
with one or more of the other points. In many localities in 
the south (Dondra Head, for example) all four are coincident. 
Near Wellawatta A and B are close together, C is about a 
quarter of a mile from B, while D is situated some considerable 
distance inland. When A, B, ©, and D coincide little or no 
evidence of land movements is observable, the best conditions 
for geological observations are obtained when all four points 
are well separated. A, B, C, and D are situated on shore 
lines. 
Besides the deposits of the Wellawatta section enumerated 
in the Introduction, two others are to be considered. ‘The 
first of these is the plateau gravel which caps the low hills in 
various localities; the second is an ancient beach which 
occurs between points C and D. 
The plateau gravel was deposited before the minor configu- 
rations of the solid land were developed, and the relationship 
