SECT. IV. 
Damps. 
24 NATURAL HISTORY 
the force of gunpowder by the proportion at leaft or two to one. 
Rarefied vapour is of great ufe in Cornwall, and enables the miners 
to get rid of the Water of their deepeft works by means of the fire- 
engine (as will be more particularly fet forth in the fequel) ; an 
engine which atfts more forcibly and conftantly than any other 
Hydraulic machine hitherto invented. 
Water having been now confidered in its moft minute Hate (that of 
rarefied vapour) it muft next be obferved, that damps rifing in our 
mines oftentimes fo affecft the miner that he cannot woik, neither 
will candles burn. This generally happens when the workings are 
cot to any great diflance from the communication with the open air ; 
and the reafon is this : Vapours are thrown up by the heat of that fire 
which all bodies more or lefs contain in themfelves or receive from 
other bodies ; but in a deep mine they cannot rife much above the 
furface of the ground, becaufe there is not air enough in the paffes 
of the mine to buoy them up, confequently they are too moift for 
refpiration, becaufe they want a fufficient mixture of air ; neither can 
they yield that inflammable nourifhment to the candle which com- 
mon air by its own elafticity, and its mixtures of oil, earth, and 
fulphur, at all times does afford ; fo that the flame is ftifled, being 
equally unable to throw ofi the parts which are burnt, and to pro- 
mote a frefh fucceflion of oily parts requifite to feed the fire. 
Thefe fluggifh damps are greater or lefs obftrudtions to the work- 
men, according to the moifture or drought of the ground : they 
have nothing pernicious, generally fpeaking, in their own nature ; 
they reft near the bottom, and incommode merely for want of an 
atftive air to difpell and raife them higher. Sometimes indeed thefe 
damps are infeded with mundic, and are then very unwholfome, 
creating naufeatings in the ftomach, and in a few weeks making the 
vifage fickly and wan ; but I never yet heard of any damps in our 
Cornifh mines fo venomous as to be immediately fatal ; the reafon 
of which may be this, that moft of our mines yield a current of 
Water in the bottom ; this ftirs and carries off the damps, and pre- 
vents their ftagnating into a thicknefs which clogs and flops all vital 
motion. In order to admit the air, a pipe or funnel of framed 
timber, about nine inches fquare, is ufually fixed, and reaches from 
the top to the bottom of the mine ; and when the damps are thick 
and ftubborn, the air is aflifted in its defeent by a bellows applied to 
the pipe. But this is a very flow and infufficient remedy where; 
any dangerous damps are apprehended. Much more effectual it is, 
according to a modern author k , to throw from you as far as poflible 
1 Muffchenbr, p. 429. Se£t. 873. 
k Letter to Mr. Hoofon, author of the Miner’s 
Dictionary. 
into 
