DAM P. 
the prefence of the damp may be confidered as certain; yet 
the human being may breathe, though not ei perfect ee 
dom, in air fo far vitiated as not to 
ly part o Ww va at the fame time, they con- 
clude that the air is utterly unfit for re{piration; but if the 
nger after the 
of ame, then they think it not very dan- 
gerous to defcend into the place. 
On account of the fuperior gravity of the carbonic acid 
nee t 
fox or milt, and this 13 pat ae y the cafe in a cavern near 
Permo nt. 
It frequently happens that the ftratum of carbonic acid 
two or three feet; fo that a man will 
as he remains in a ftanding po- 
€ an to lie down or to fit, he 
d run the rifk of being fuffocated. 
he fudden iffue of this damp out of the earth, efpecially | 
when any digging has been performed, has fometimes in- 
ere killed the workmen. 
In all fuch cafes, ventilation (in whatever manner it may 
be praétifed) is the beft method of diffipating the damp. 
But fhould a man be obliged to go down into a place thus in- 
fe@ted, either for the purpofe of faving another man, or for 
fome other particular purpofe, he — do well to filla 
bladder with common air, and by s of a fhort 
faitened to the neck of the bladder, and he d in his 
to breath 
mig 
fille dw eae on and furnifhed with ftop-cocks, or 
merel y mh tubes tto: see with corks 
Cautious miners ought always hi have fuch para or 
ae ike bags, “fil led with common air, b r they 
little or nothing, and will effectually fave ae lives 
occaiiona si 
hen digging is to be performed in any place where the 
leat fufpicion of a fudden iffue of the choke-damp is en- 
tertained, it will be proper to keep a candle or lamp burn- 
ing clofe to the ground; for if any noxious gas happens to 
come forth, the ac out of the flame wili afford {ufficient 
warning to the wor 
The fudden iffue of f the choke-damp from the earth ae 
quently occurs in the neigbourhood of volcanoes, upo 
lavas, al old accumulation of afhes or other volcanic pro- 
du€ ete — this fort ta ce in th 
san of mount Vefuvius, in les, where the noxious 
t 
vapouts, called ue = the inhabita.ats,) {uddenty enter 
houfes, cellar to the great ann oyance ot the inhabi- 
tants, who, a5 Be as other animals, are fometimes killed 
by them. See fir William Hamilton’s various accounts of 
the mount Vefuvius and its eruptions, 1p Philofophical 
a for 30 or 40 years pait. of the ferenti- 
the above-mentioned aut have occalional- 
ee 
but more or lefs mixed witha 
companied with fulphureous ae eet rfenical § vapours. res 
markable inftance of a contiaual ftream of carbonic ‘acid gas 
iffuing from the ge occurs near the city of Naples. At 
about five or fix miles from that city, near the foot of a 
hill, there is a Sneen cave called rotta del cane in the Ita- 
lian Janguage. This grotto is About fourte 
nearly feven eet high at the ent 
rance. 
it, which is nearly on the fame level ~-i-4: the nt ex 
tern round, there is at all times a ftratum of carbonic 
themfelves in 
this were at times found dea in it, in confequence 
of whi ich a dec laced to the aperture of it, which is 
now only opened occa onally. e experiments lually 
this grotto, are, that of 
bringing a lighted torch or lighted piece o near the 
bottom or floor $ ; the flame of whic n 
as it comes within } 
The re{piration of the animal 
is inftantly affeered, igs its ftrengta fails, fo as to remain 
ag entiy dead ; on being cxpofed to the ambient air 
t of the paar ae if it be not too far gone, the peor anie 
ad will ee. recover its ae tion a 
fro 
are very — confider: ring the tim 
were made. Gh (cuves: that the sacks of a candle, ex- 
tinguihed near the bottom of this grotto, is entirely retain- 
ed within the ftratum of gas; and that if part of that 
e happened to be driven Git of the grotto, it defcended 
like water falling from the edge of a tub. Had oe hares 
acquainted with the nature of carbonic acid he 
would have eafily underftood that the fmoke was ree 
ingenious perfon relates another Sepermen which tends to 
prove the acid quality of the gas concerned, w ich quay 
has long after been fully ine. e an 
nions placed the head of an alembic on the bottom o 
evident that the head of the alembic condenfed the watery 
paiticles from the air of the grotto, and thefe became aci- 
nce of their 
gas. e ground 1 
of grotto del cane thews manifcit figns of fubterranean fires 
or fermentation, as it oe with fulphur, hot {prings, 
emanations of {mo 
bad -datp, tough “okies ably heavier than pure hy- 
gen gas, is yet ighter tnan atmofpherc air. aaag 
where a ee ble veatiation is kept up, it feldom accumu. 
O. 
2 
he 
3) 
<7 
th 
te 
-O 
C 
5 
= 
= 
— 
ao 
S 
lates angerous amount in the fhafts, or acc pits, 
that are ; but in the horizontal gaileries 
where it occ cupies ies cae er part, forming a fratum, lying 
immediately in contaét wit! f. At generally m iy 
its firft ane in the cracks and crevices of the coal 
6 pa rticularly 
