OF CORNWALL. i 53 
of the lode was the perpendicular, or nearly jfo, and the inclination 
and fradtures are but two different degrees of variation from it. If 
therefore we can difcover the probable caufe of the inclination of lodes, 
the fame caufe, allowing it but a greater impetus, will account for 
the fra&ure. Now betwixt the inclination of lodes, and the dippings 
of the adjoining Jlrata , there is oftentimes (tho’ not always) fo ma- 
nifeff an agreement and correfpondence, that whatever occafioned 
the latter could not but produce the former. Let us firff note the 
dippings of the Jlrata ; for if they have alfo been wrefted, the 
lodes contained in them could not have preferved their Ration. As 
the original pofition of lodes was perpendicular, that of the Jlrata 
was horizontal, each layer of Rone, earth, fand, gravel, and their 
commixtures, reRing (for the moR part) according to their differ- 
ent gravitations, and fprcading in belts and floors nearly parallel to 
the furface of the earth ; but we often find thefe Jlrata very fenfibly 
declined from that, their firff pofition ; nay fomctimes quite reverfed, 
and changed into perpendicular. Thus, for infiance, the rocks 
and ledges on each fide of large rivers, laid bare by tides, are fre- 
quently obferved to turn their points and thin edges down towards 
the chanel, intimating, that, from horizontal, they have dipped 
forward towards each other, making an angle in the middle, in 
which the waters pafs, as in Plate XVII. Fig. i. page 149. Again: 
In finking on the fides and bottom of vallies, we find the natural 
rock or karn, G, H, F. (Fig. 11. ibid.) equally covered with earth 
and rubble, and running nearly in a plane parallel to the furface of 
the ground. For infiance, at the hill, E, the karn fhall be ten 
feet under the furface; in the bottom C, it fliall be fomewhat 
deeper, that is, more covered by what is waflied off from the fides; 
and as it coaffs upwards again to the hill D, it fliall be buried only 
ten feet again, as at F. Now the lode which croffes fuch vallies, 
rifes and falls, as the karn G, M, H, which cannot therefore be the 
natural firff fite either of karn or lode; for it is utterly impoflible, 
that any fifiure, being an open chanel, could contain in its fides 
M, L, K, any liquid (which all lodes muff at firff have been) if 
they were formed in fuch a curve-line ; as much as that a fyphon, if 
the tube was flit and open on one fide, fhould draw water : this 
obfervation therefore will lead us to this further truth, that the fub- 
fidence of Rich vallies muff have happened fince the formation of 
lodes, and that the Jlrata , in many inftances, have departed from 
their primary pofition ; which was to be fliewn. But the Jlrata have 
not only dipped in iome places lefs, in lome more, but from hori- 
zontal have become perpendicular. Now, when we fee a wall 
lean, we conclude immediately that the foundation has given way 
according to the angle which the wall makes with the horizon ; and 
R r when 
