20 
THE GEOLOGIST. 
siderable depth, from which large quantities of sand are continually 
carted for the purposes of ballast or manure. Otlier sections, similar 
to the above, are to be found further inland, the most interesting of 
which is that in a pit by the side of the road on the Green leading 
towards New Quay. The stratum of sand there is not, it is true, more 
than six inches thick, but lying, as it does, under about eight inches 
of soil, upon one of the highest points in the island, the section is 
valuable, as showing that, in all probability, at one time, the whole of 
the surface of the island has been capped with sand, which has been 
washed away from those portions where it is now deficient, leaving the 
underlying stratum of brown clay visible. The section in this pit I 
estimated as follows : — 
Surface Soil, 8 inches. 
Fine White Sand, 6 inches. 
Brown Clay, 2 feet. 
" Ram," or coarse grit, 7 feet. 
Granite. 
The stratum No. 3 prevails very widely over the whole island, 
coming to the surface in all the lower lands, and forming the great 
bed in which agricultural and gardening operations are carried on. 
I traced it completely across the island to Tolman Point in one 
direction, and to Watermill Cove in the other. Its dark colour is in 
all probability due to the large proportion of oxide of iron which it 
has derived from the chemical decomposition of the mica of the disin- 
tegrated granite. No. 4 is a very instructive bed as developed in the 
various sections in which it is brought to light. It gives a thorough 
insight into the mode by which the apparently solid granite has in 
the course of ages been broken up and crumbled, and thus gradually 
submitted to the action of the elements, until its constituent parts 
have been resolved into strata serviceable to man. In many places 
within these islands, may be traced the several stages of decomposi- 
tion, from solid masses of granitic rock, to broken fragments, thence to 
crumbling rubble, and to coarse granitic sand, and the final passage 
into aluminous and siliceous earth from the degradation and decompo- 
sition of the felspar and quartz, in many places tinged deeply with 
the oxides of iron from the decaying mica. That the islands have been 
several times submerged, during the course of these successive changes 
