OF CORNWALL. 75 
of bogs x ; and where this covering is thin, the fands are dangerous 
in proportion to the depth of the bogs underneath. Where the 
fands are only quick at particular times, as at Heyl in Penwith, and 
on the brand betwixt Penzance and Marazion, and elfewhere, the 
alteration is owing to wind and fea : in calm weather, fands fettle, 
grow firm and compact ; but a violent ftormy fea will ftir and fhift 
the jlratum of fand, condenfe and accumulate it in fome places, 
and in others leave the jlratum fo rare and diluted, that it cannot 
bear the weight of man or horfe, which muft therefore fink into 
thofe places whence the fand is dilperfed, till they come to that 
which has not yet been moved by the ftorm. 
In fome places, but particularly in the parifh of Conflantine, sect, vil 
in Cornwall, may be obferved a jlratum of gritty large-grained fand, m 
fpread under the vegetable foil, on the top of the Jlrata of moor- 
ftone ; for that our moorftone lies in jlrata , notwithftanding any 
aftertions to the contrary, will be fufiiciently proved in the following 
pages. This fand is exactly of the fame colour and fubftance as the 
moorftone below it ; fo that, till it is furred from its natural pofi- 
tion, to the eye it appears as moorftone. Some Naturalifts have 
fuppofed this fand to have been fretted off from the moorftone, on 
which it lies, by the waters of the univerfal Deluge ; but ( fuppofing 
the waters of the Deluge of fufficient force to have effected fuch a 
feparation, which is far from being agreed upon) upon examination, 
thefe fandy particles in a microfcope feem too fharp and angu- 
lar to have undergone fuch a trituration : befides, they are not placed 
Ipecifically, as to weight and fize, with large rounded pebbles in- 
termixed, as they would have been if they had been feparated from 
the furface of ftones, and afterwards depofited by the waters of the 
Deluge : I fliould therefore rather imagine thefe fands to have been 
natural, and fome of the primary concreted materials of which 
moorftone appears to have been formed, and that moorftone confifts 
only or the fame grit, cemented into ftone by a cryftal bafts ; that 
the bafts, which forms all ftone, was more abundant below in the 
bowels of the earth, than near the furface (as appears by the gene- 
rality of Mils being of a more compact confidence the deeper we 
dig) y ; that, from a deficiency of this cement or bafts near the 
furface, as well as the interfering powers of air, heat, and cold, this 
fandy grit never was fixed into ftone, but always remained in the 
prefent incoherent ftate. 
But the fituation of fands moft difficult to be accounted for, sect.viii. 
according to the theories at prefent moft favourably thought of, IS Sea-fand 
1 above Sea- 
x Thus the ftrand at Youghall, in the county turf-bog, covered with fand and pebbles. Hilt. mar!c - 
of Cork, Ireland, is no more than a common of Cork, page rog. 
y See before, pag. 71. 
that 
