THE BASALT OF ROWLEY REGIS. 
129 
soil, only three to nine inches, being hardly worth notice ; 
while on south and west our section would be— 
Basalt at base, 
Roche above, obscured by till or bed of 
Native blocks, and covered by 
Surface soil as before ; 
thus accounting for the waste or degradation of the bill tops, 
and pointing out the direction from which the degrading 
forces proceeded. 
I think in the above we have another proof of the roche 
being in its original condition, for we find it of precisely the 
same structure, and arranged similarly to where it lias no pro¬ 
tecting covering of till. Where it is not so covered (on the 
north and east) the beds are no thinner, i.e., disintegration (?) 
has not proceeded more rapidly or done more work than on 
the south and west where it is thickly covered, well protected, 
and the material itself is not any more friable, more decom¬ 
posed, or “ rotten,” than where such covering protection 
obtains. 
We now come to consider the clay-marl, and this subject 
opens a much wider field than that we have just been 
discussing. 
The clay-marl covers a very considerable area on either 
side the centre line of eruption, and as it is abundantly 
evident that it results from the degradation of the roche, and 
from this cause solely, we should expect to find it thinnest a 
little below the shoulders of the hill, thickening as we descend 
to the valley bottoms, and again thinning out to nothing as 
we approach the outer margin of the deposit; and as a matter 
of fact this is really what is found. 
This high land must have been considerably higher at the 
close of the eruptions : first, by reason of the great thickness 
of roche overlying the present tops, and, secondly, by reason 
of the much greater depth of the surrounding valleys, sub¬ 
sequently filled with the degraded roche. 
The outer margin of the clay-marl area we may take 
generally as being about one-and-a-half miles on either side 
of the axis of eruption, and this axis lies as near as possible 
due north and south. The outer margin of the deposit is 
obscured for the most part by two series of drift-clays and 
gravels; the earlier being the ordinary boulder-clay of the 
district, including gravels and boulders derived from the 
Bunter conglomerate, and the later (gravel and clay) is a 
local re-wash of the surface deposits and outcrops of local 
rocks and measures existing at the period of a later deluge. 
There is evidence high up on the hill sides that one of these 
