i 3 4 NATURAL HISTORY 
of the vitriol with which it is impregnated, very foon ; fo that, in 
our hydraulic engines, the piftons of the pumps in copper-mines 
muft be made of brafs, or they are eaten away and become ufelefs 
in a little time. 
sect. xi. Mundic mixed with earth will deftroy all vegetation, its falts 
with earth< being too acrimonious and fiery to enter the finer veffels of plants 
without rending and utterly fpoiling them ; for which reafon the 
mundic, pulverized at the ftamping-mill, is carried off to mix with 
the fea-gravel and clay, and effectually prevents all grafs and weed 
from growing in gravel-walks. 
sect. xii. Fire has a much worfe effeCt upon mundic than the other ele- 
witJi fire, ments, and throws it into its moil fatal ftate ; for when it has been 
fomewhat burnt, and the fulphur which fheathed the poifonous 
fpicula of arfenick is difperfed, the arfenick acts without reftraint. 
In the management of the furnace, called the Buming-houfe, great 
caution muft be ufed : the arfenick, which flies off' from the ore, 
has feveral refts and paufes ; it fixes upon the ftem and head of the 
iron rake which ftirs the tin, in bunches of white-yellow duft ; 
and here it is reckoned moft poifonous, as being leaft mixed ; but 
it is alfo ftrongly poifonous from the bottom of the flue of the 
chimney upwards, where, although it is a mixture or mundic, ful- 
phur, and foot of pit-coal as well as arfenick, it is yet fo fatal, that 
a perfon of an adjoining parifh to Ludgvan, rafhly looking down, 
and prying into the chimney of one of thefe Burning-houfes, was 
feized inftantly in fo violent a manner, that, notwithftanding all 
proper afliftance, he foon died. The workmen are oftentimes 
obliged to fweep out thefe furnaces and clear the chimney, a fervice 
of no little danger ; it is ufual therefore to put a cloth before their 
mouth and nofe when they are upon this duty ; but Elijah Bond, 
a youth of the parifti of Ludgvan, fweeping out what they call the 
oven, (the place where the tin-ore lies roafting) at Rofmgrows 
Burning-houfo, January 25, 1750, without the necefiary precau- 
tions, was taken ill immediately, and, though he had the ufual 
remedy of oil given him, he died that evening. 
sect. xni. The fmoke of burnt-mundic when it leaves the chimney being 
more difperfed, is not foon, but as furely fatal to all tender herbs 
and plants, and bees of the adjacent neighbourhood, as it lights 
upon them ; and the fire-men, who attend this procefs, greatly 
impair their conftitutions, if they make it their foie and conftant 
employment. 
The 
