x 5 8 NATURAL HISTORY 
in its original perpendicular polition, and M F a Jiratum fpread on 
any precarious foundation to give way and defcend to RLF, then 
will the lode N F defcend alfo, and become O E F. A piece of 
the fame Jiratum , R L, is afterwards unfooted, and becomes S I K, 
then will the lode, O E, fall in proportion, and become PCD. 
Another fubfidence happens from like concurrent caufes, and S I 
fhall become G H ; then fhall that portion of the lode, P C, fall 
into the polition of A B, and, in proportion to the times and 
falls of the under Jlrata , fhall the lodes defcend either in whole or 
in part. It may be faid, that if thefe fubfidences were the caufes of 
the above-mentioned fradtures, then the interftices of fuch broken 
lodes would be filled by earth, clay, gravel, and fuch loofe materials, 
as the difordered Jlrata could not but throw into the opened cre- 
vices ; this is very true, and the matter of fadt confirms the fpecu- 
lation ; for between B and C, D and E, ( ibid.) a fhelving foft con- 
geries of rubble, clay, land, or the like, (by the Cornifh called a 
Flookan) is interpoled: it is of a different fubftance from the 
lode and wall of the filfure, and by the vulgar is thought the caule 
of the lode’s being ftarted ; but is indeed the effedt, and nothing 
more than the depofite of the adjoining grounds after the fradture 
of the lode had been made. 
sect. xr. As we have endeavoured to Ihew that the fubfidences of the 
Caufe of the jlrata were the caufe of the inclination and fradture of lodes, it can- 
the f ftrata! ° f not be improper to hint at the date and caufe of thele fubfidences. 
It has Been obferved before, (page 80) that, at the firft indura- 
tion of bodies, it was impoflible, but that the furface of our globe 
fhould be higher in fome parts, and lower in the reft ; that the 
earth, porous and cavernous as it mull be by the intermixture of 
fubftances apt to give way, ferment, and explode, mull fink deep 
in fome places, and lefs, or not at all, in other places. Now, as 
we owe the mountainous and hilly parts of our globe to the folids 
which flood firm and prominent, fo to thefe deprelfions of the more 
lax and cavernous parts we owe the bed of the ocean, and the fub- 
fidence of vallies ; but thele deprelfions, fo neceflary, ( the lefler to 
condudt the rivers, and the greater to contain and form the fea) 
could not but influence more or lefs all the adjoining Jlrata , and 
the Jlrata all their fifiures and lodes ; hence fo manifeft a relation 
in many parts to thefe firft and principal deprelfions. 
Secondly, When the fea was formed, its fearching fludtuating 
waters walhed and exhaufted the loofer fubftances from betwixt the 
Jlrata , and time occasioned many fubfidences of the higher upon 
the lower Jlrata , which fubfidences mull have been in fize and 
tendency according to the Ihape and dimenfions of the vacancies 
from 
