OF CORNWALL. 25 
into the fufpeded or tainted pit, two quarts of fpiritus urinofus 
volatilis, which will occafion fo great a rarefaction as to overpower 
the poifonous vapours, and for a long time lupply the want of 
air ; the miner taking care not to venture into the pit till twelve 
hours after the infufion. Dr. Plot’s propofal 1 * * is more eafily executed. 
He adviies, that one peck of unflacked lime may be thrown into 
fuch fufpeCted place, w 7 hich flaking in the Water, and fuming out 
at the top, will fo effectually difpel all poifonous vapours in a little 
time, that there will be no further danger. Thefe may ferve for 
temporary expedients, but the molt effectual, though expcnfive 
remedy is by a frefh fhaft , to open a communication betwixt the 
drift and the common air. 
The Dews in Cornwall are not remarkably noxious to either 
herbs or animals, which I attribute to our having no long calms, 
nor lafting fogs. & 
SECT. V. 
Dews. 
_ ^P r * n £> s k e divided into fimple and mineral. Simple Spring- sect, vi. 
Water may be confidered either as fuperficial or fubterraneous. Springs and 
By the fuperficial, I mean thofe Springs which rife out of, or theirOrigine. 
iflue from, the lurface of the earth; by the fubterraneous, thofe 
w ic 1 have their chanels deeper, and their courfes longer under- 
ground. That fuperficial Springs are the effeCts of rain and dews, 
cannot well be difputed, when we fee their encreafe and decreafe, 
according as the feafon proves wet or otherwife ; but whence the 
fubterraneous, and thofe which feel no alteration from the feafons 
derive their origin, has employed the enquiries of the curious, and 
hitherto divided their fentiments. Some think them owing to fub- 
terraneous heat; and no one labours more ftrenuoufly for this opi- 
nion, than the learned Morton, in his Natural Hiflory of North- 
ampton! ir^-, who has not only adopted what others have produced 
or t le ettei confirmation of this hypothefis, but has produced 
evera t ermometrical experiments of his own, in order to eftablifh 
it. He derives Springs (conftant Springs more efpecially) from 
vapours thrown up by fubterraneous heat “, and thinks his obferva- 
tions mamfeftly fhew how the Water of fuch Springs is fupplied. 
is arguments are drawn from the heat people feel at their firfl 
entering^ the pit or well, which heat encreafes manifeftly as they 
- cend . “ That wells in fand are hotter than any other of like 
i , and that the next degree of heat in wells, is in thofe cut 
m o a roc k : That the faintings which feize the workmen, are 
1 Oxf. page 63. 
call a "fhaft , * t ^ we de fcend into mines we 
n Northamptonfliire, page 206. 
0 lb. 297. 
H 
owing 
