THE CABOOK OF CEYLON. 
421 
x.x] 
It evidently belongs to an earlier geological period than the 
Quaternary, for it is older than the recent formation of valleys 
and rivers. The cahook often contains large, rounded, un¬ 
weathered granite blocks, quite resembling the rolled-stone 
blocks in Sweden. In this way there arise at places where the 
cahook stratum has again been broken up and washed away by 
currents of water, formations which are so bewilderingly like 
the ridges (osar) and hills with erratic blocks in Sweden and 
Finland that I was astonished when I saw them. /I was com¬ 
pelled to resort to the evidence of the palms to convince myself 
that it was not an illusion which unrolled before me the well- 
known contours from the downs of my native land. An accurate 
study of the sandy hills on the Inland Sea of Japan, of the clay 
cliffs of Hong Kong, and the cabook of Ceylon would certainly 
yield very unexpected contributions to an explanation of the 
way in which the sand and rolled-stone osar of Scandinavia 
have first arisen. It would show that much which the Swedish 
geologists still consider to be glacial gravel transported by water 
and ice, is only the product of a process of weathering or, more 
correctly, falling asunder, which has gone on in Sweden also on 
an enormous scale. Even a portion of our Quaternary clays 
have perhaps had a similar origin, and we find here a simple 
explanation of the important circumstance, which is not suffi¬ 
ciently attended to by our geologists, that often all the erratic 
blocks at a place are of the same kind, and resemble in their 
nature the underlying or neighbouring rocks. 
/It is this weathering process which has originated the gem 
sand of Ceylon. Precious stones have been found disseminated 
in limited numbers in the granite converted into cabook. In 
weathering, the difficultly decomposable precious stones have 
not been attacked, or attacked only to a limited extent. They 
have therefore retained their original form and hardness. 
When in the course of thousands of years streams of water 
have flowed over the layers of cabook, their soft, already half- 
