I4 8 natural history 
fo will the lode be for the moft part. Again, the fubftance of the 
lode is obferved to be frequently the fame, at the fame level and 
depth with that of the jirata ; but though there is oftentimes fuch 
an agreement betwixt the lode and the jirata near it, ii is iar from 
being always the cafe : in the Mil grammar there is no general 
rule Without many exceptions, experience convincing us, that fome- 
times lodes are both as to colours and textures, as well as impreg- 
nation, entirely different from the adjoining jirata y . However, 
the general refemblance betwixt the lode and the ground adjoining, 
may probably conduct us to the true origine of lodes ; for as loon 
as the fiffures were made by the contraction of the jirata , what- 
ever did not join the hardening mafs was carried off' by the exprejj'ed 
moifture into the adjoining fiffures, the waters depofiting what they 
brought with them where-ever a proper nidus , or fufficient attraction 
to arreft it, occurred ; that the little collateral veins are oftentimes 
filled, and at the lame depth with like fubftance to the mafter-lode, 
will convince us that they were filled at the fame time, by one and 
the fame caufe, and from one common repofitory. The contents 
then of the fiffures proceeded from the neareft jirata } and ft the 
openings of the Jirata into the fiffures were horizontal, then the 
cavities were filled at equal depths with the lame fubftances \ but if 
the communications were in any other direction, as frequently they 
muff needs be, and indeed are fo found, then the depofited matter 
is not found at equal depths in jirata and fiffure, but higher or 
lower, in fuch quantity and direction, as the vacancy of place, the 
oppofition or compliance of other bodies, and the refpective gravita- 
tions of the adventitious matter, lhall have diftributed it. 
sect. hi. That part of the lode which is inclofed betwixt the two walls of 
Of the broil ^ fiffbre, is called the body of the lode, but the fiffure ending 
o^top of the t | ic k arn ffe lode has its top covered over with a parcel of 
loofe ftones and earth, ufually of the fame impregnation, though 
in a lefs degree, of the fame colour and cement as the lode,^ and 
this in Cornwall we call the broil of the lode. See Plate XVII. 
Fig. vii. D. p. 149. This broil not being confined betwixt walls, as the 
lode is, is frequently found to have been difturbed, and fometimes 
wholly diffipated, efpecially when the walls of the fiffure reach up 
to day, as they do in naked karns ; but where there is a layer of 
rubble or ftiff deep clay above the fiffure, which is much oftener 
the cafe, then the broil is always found covering the lode, and 
y Hutchinfon is therefore too general in his fol- ftrata, there are ever the like in the fame depths 
lowing obfervation on the ftrata of Cornwall, in the vein ; that of the vein, being ever of hke 
Trails, page 86. “ Where the fpar and the talk kind with that of the ftratum.” 
happen to be different at different depths in the 31 That is, the rocky ftratum. 
brooding, 
