OF CORNWALL. r 5 x 
Sixthly, That the angles of thefe ftones are blunted, proceeds 
evidently from the agitation of water, and they are fmoothed in 
proportion to the diftance they have been rolled ; and had the force 
continued a fufficient while, thefe ftones would have been as round 
as the pebbles on the fea-fhore ; but the farther we find them from 
the lode, the more trituration they have undergone, and vice 
verfa . 
It may be here objected, that if the deluge Smoothed off the 
angles of thefe fhodes, why had it not the fame effect upon the 
loofe parts of the killas, granite, marble, and other ftones with 
which thefe fhodes are intermixed ? The reafon feems to be this : 
The long, flattifh, light, and fharp-angled parts of the broil con- 
tinued their former fituation on the top of the lode ; they could 
not but be wafhed, yet they were not detached : thofe parts only 
of the broil which were ftony nodules, impregnated with metals 
and minerals, upon every agitation rolled, and fell with forces in 
proportion to their weight ; whereas lighter and flatter ftones moved 
with lefs violence, and fuffered little as to their extremities. This 
was the cafe in general ; but where declivities were long rather than 
fteep, and many little vallies concurred and difeharged their con- 
tents, there, the force of the waters being increafed, not only the 
tin-fhodes are much rounded, but the granite and killas nodules ; 
and every kind of ftone, from a foot diameter and under, is rounded 
into a pebble-like form, as well as the tin, as any one may fatisfy 
himfelf by obferving the Jlrata of rounded ftones in the ftrearn- 
works of St. Auftel moor. Shodes therefore are not always metallic ; 
they are fometimes barren. One thing more may be here obferved, 
which is, that the broil is feldom fo well impregnated as the lode 
underneath ; the reafon I take to be this : The broil, being more 
loofe and fhattery than the lode, has had much of its tin wafhed 
away by floods, whereas the metal of the lode lay more fecure 
from fuch diftipation. Again : The broil being in pofttion above 
the walls of the fiftures, had no depth of Jlratum to draw the me- 
tallic particles from, had no chinks or collateral crevices for the 
Waters to communicate the treafures of the adjoining Jlrata , nor 
fiffure to lodge and detain them : this is alfo the reafon that the 
upper parts of the lode itfelf are feldom fo well impregnated as thofe 
parts which lie deeper in the fame vein, infomuch, that it is a com- 
mon rule with the miners to fink upon lodes which are poor, it 
being generally found, that lodes prove richer in depth, than near 
the furface. 
From the top or broil, let us defeend, and take notice of the sect. v. 
moft remarkable properties of the body of the lode. rf f the e iode dy 
The 
