j 68 N A T U R A L H I S T O R Y
is often deep anè manyv
Anciently; they- worked - for tin,.(efpecially when found difpofed m
floors) by kyihg open all the: ground, as (they now do in fton^quar-
ries; feveral of- thefe:openings (called (3offens) aj-e ftill to be feen
in the parifh of -St. Juft, and elfewhere.; but this being a method
too operofe and expenfive, it was not long, we may imagine, before
the tinners learned to make paflages into the bowels ,o f the
earth, of dimenfions no more than neceffary to examine the lodes,
and bring off the ore.; and this is, what is properly calléd; mining.
The arts neceflary to mining are many, and every mine almoit
requires a peculiar management:. mining therefore muft be learned
by pradife, by experience, and maffers; not from books,: the rules
of which, though ever fo juft, muft be frequently fufpended, altered,
-qualified, and fuperfeded, according as the various circumftances
require. Rather than attempt any direöions, I chufe to give a defcnp-
tion of oneconfiderable mine from an aftual meafuremerit, intending
that the reader may-have a clear: notion o f the manner in which
our Comifli mines are at prefent carried raj,
s e c t . xi. Fig.-i. is the fe&on of the pool-mine, exhibiting dto feveral
Explanation parts, and the underground workings. | j | / r . ^
f S § § ! a black-ore fhaft; B, houfe f o a f t C, fire-engine, fouth front;
North-houfe fliaft; Ë, Little North-houfe;fhaft; E, Penhelic-
houfe {haft; G, Water-Whim fliaft; H, Roflceer fhaft; 1 1 1 , the
main adit, or principal drain ; R , fire-engineftiaft; L L L, Hnel-
dudnans lode when firft difeovered in fingle dots ; M, Penhelic lode
in double dots; N, South-houfe winds; O, hollow cyUndersXfome
iron, fome of brafs) through which the fire-engine, C, draws üp the
water tSat it may run off through the adit, I I ; P, the-fevera! workings
oh the fouth lode, called HueLdudnans, as they ftood in the year
174 6; Q, a drift to carry the. water from the north lode to the bottom
o f the engine-ftiafr, X, on the fouth lode; R, bottoms o f the
great North-houfe on Penhelic lode, dotted; S, a dippa or pit with a
force-pump to free the water ; T , bottom of Huel-dudnans; Y ,
Pen-helic deep bottom; W, little winds, that is, finall {hafts made
from a drift in purfuit of the ore,' and leading down to R X,:the
bottom of the fire-engine {haft, from whence the water of the
whole mine there gathered together by various drifts and landers,
or gutters o f wood, is drawn up to the main adit, I ; Y , grey-ore
{haft on the fouth lode.
O f Fig. n. Fig. n. exhibits the plan of the two lodes worked by the pool-
ibid. mine; fe tbe north or Penhelic lode in dotted lines; i } fouth or
Huel-dudnans lode; c> black-ore {haft; <2, houfe-fhaft; e, engine-
{baft, and fummer-pole {haft; / , drift for the water of the northlode
;