[ 219 ] 
rit ; on which their chief virtues are found to de- 
“ pend: and that fome of thofe waters feem to be 
“ impregnated with exhalations that nearly refemble 
the fulminating-damp 5 which, by its expiohons, 
“ is found fo deflrudtive in coal-mines : while other 
“ waters are more evidently fiturated with that mod: 
‘‘ fubtile and adlive exhalation, which, in many 
“ places, perfpires from fprings and lakes, and other 
openings of the earth ; or arifes in pits and mines, 
“ where it is difcovered by extinguishing flame; and, 
“ from its pernicious effedts, in killing all animals that 
“ breathe therein,, is known to our iriiners by the 
“ name of choak-damp.” 
This mephitic exhalation I, long ago, difcovered 
to be a particular kind of air, or permanently elaffic 
fluid ; and, from various obfervations and experiments 
related in the above-mentioned ^ effays, had reafon 
to conclude, that it enters the compofltion of the wa- 
ters of <Pyrmont and Spa, and of all others vyhich, 
from their fharp and pungent tafle, are fliled acidul(B ; 
and that it conftitutes the volatile principle of thofe 
waters, called their fpirit, on which their prime ver- 
tues chiefly depend ; altho’ it hath, hitherto, evaded 
the enquiries of the mofl; fkilful chemifts, who have 
not been able to retain it in their veflfels j neither have 
they difcovered any method of imitating it by their 
^rt 
In order the more fully to afcertain a fadl of fuch 
importance, and to obtain a clearer knowledge of the 
nature of this fpirit, I took the opportunity, while 
lately at Spa, to make a few experiments on thofe 
•* See Extra£t from E% the fourth, which is puhlifhed after 
thefe experiments. , 
p £ 2 celebrated 
