natural history 
is often too little and vain, where the workings are deep and many. 
Anciently they worked for tin, (efpecially when found difpoled in 
floors) by laying open all the ground, as they now do in (tone-quar- 
ries ; feveral of thefe openings (called Coffens) are 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, >e- 
fore the tinners learned to make paffages into the bowels or the 
earth, of dimenfions no more than neceffary to examine the lodes, 
and bring off the ore; and this is what is properly called mining. 
The arts neceffary to mining are many, and every mine almoit 
requires a peculiar management: mining therefore mint be learned 
by praftife, by experience, and mafters; not from books, the rules 
of which, though ever fo juft, muft be frequently fufpended, alter- 
ed, qualified, and fuperfeded, according as the various circumftances 
require. Rather than attempt any diredions, I chufe to give a defec- 
tion of one confiderable mine from an adual meafurement, intend- 
ing that the reader may have a clear notion of the manner in which 
our Cornifh mines are at prefent carried on. 
SECT. XI. 
Explanation 
of PI. XVIII. 
in the follow- 
ing page. 
Fig. i. is the fedtion of the pool-mine, exhibiting its feveral 
parts, and the underground workings. 
A, black-ore fliaft ; B, houfe (haft ; C, fire-engine, fouth front ; 
D, North-houfe fliaft; E, Little North-houfe fliaft; F, Penhelic- 
houfe fliaft ; G, Water-Whim fhaft ; H, Rofkeer fliaft ; III, the 
main adit, or principal drain; K, fire-engine fliaft ; L L L, Huel- 
dudnans lode when firft difeovered in Angle dots ; M, Penhelic lode 
in double dots; N, South-houfe winds ; O, hollow cylinders (tome 
iron, fome of brafs) through which the fire-engine, C, draws up the 
water that it may run off through the adit, 1 1 ; P, the feveral work- 
ings on the fouth lode, called Huel-dudnans, as they flood in the year 
1746; Q, a drift to carry the water from the north lode to the bot- 
tom of the engine-fhaft, X, on the fouth lode; R, bottoms of 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 ; V, 
Pen-helic deep bottom ; W, little winds, that is, fmall fhafta made 
from a drift in purfuit of the ore, and leading down to R X, the 
bottom of the fire-engine fliaft, from whence the water of ^ the 
whole mine there gathered together by various drifts ana lanaers, 
or gutters of wood, is drawn up to the main adit, I j ^ > grey-01 e 
fhaft on the fouth lode. 
Fig. 11. exhibits the plan of the two lodes worked by the pooi- 
mine ; a, the north or Penhelic lode in dotted lines ; 6, fouth or 
Huel-dudnans lode ; c, black-ore fliaft ; d, home-fhaft ; 2, engine- 
fhaft, and fummer-pole fliaft ; /, drift for the water of the non 
lode; 
Of Fig. II. 
ibid. 
