420 
THE VOYAGE OF THE VEGA. 
[chap. 
the sea, ridges of sand {osar) with sid^s partly clothed with* 
wood, partly sandy slopes of a light yellow colour, covered by 
no vegetation. On a closer examination, however, we find that 
the supposed sandy ridges consist of weathered granitic rocks, 
in which all possible intermediate stages may be seen between 
the solid rock and the loose sand. The sand is not stratified, 
and contains large,^ loose, rounded blocks in sitn, completely 
resembling the erratic blocks in Sweden, although with a more 
rugged surface. The boundary between ^ the unweathered 
o’ranite and that which has been converted into sand is often 
so sharp that a stroke of the hammer separates the crust of 
granitic sand from the granite blocks. They have an almost 
fresh surface, and a couple of millimetres within the boundary 
the rock is quite unaltered. No formation of clay takes place, 
and the alteration to which the rocks are subjected therefore 
consists in a crumbling or formation of sand, and not, or at 
least only to a very small extent, in a chemical change. Even 
at Hong Kong the principal rock consisted of granite. Here 
too the surface of the granite rock was quite altered to a very 
considerable depth, not however to sand, but to a fine, often 
reddish, clay, thus in quite a different way from that on the 
coast of the Inland Sea of Japan. Here too one could at many 
places follow completely the change of the hard granite mass 
to a clay which still lay in sitn, but without its being possible 
to draw so sharp a boundary between the primitive rock and 
the newly-formed loose earthy layers as at the first-named 
place. We had opportunities of observing a similar crumbling 
down of the hard granite at every road-section between Galle, 
Colombo, and Ratnapoora, with the difference that the granite 
and gneiss here crumbled down to a coarse sand, which was 
again bound together by newly-formed hydrated peroxide of 
iron to a peculiar porous sandstone, called by the natives 
cahooh. This sandstone forms the layer lying next the rock in 
nearly all the hills on that part of the island which we visited. 
