frotti tl banks is no longer seen to bubble up, 
‘^'scngagenient of a gas, as it appears, from ac- 
Wci(.fg Very remote antiquity, to have done. The 
4b[^ the lake were attentively examined by the 
ttins • I 'bi waters were at the highest, and after heavy 
^ bittub^'^ could never discover a single bubble of air. 
•ttay ? cf aquatic insects which sport on the surface, 
occasion some deception ; but a slight 
'^at sup[!?*' detects tlie error. If, therefore, we do 
(jj- those authors who have described the ebulli- 
he uear the banks of the lake Agnano to 
”®beived, it must at least be confessed, that this 
has now ceased. The quantity of the sul- 
• ^'oves' ^^bbfs which rise in the contiguous stoves, called 
*'’*hi^l f Sf- Germauo, must likewise be greatly dimi- 
Pfesent s?"! anciently was : for, adjoining to the 
GROTTA DEL CANE. 
117 
Ii'?bt faK^P''b^> 've still find the remains of a spacious an- 
ii’ 
'bteri.i- ,T their direction, show for what purpose they were 
>h: 
fab ‘ 
icb, ";bh tubes of terra cotta inserted in the walls. 
®ti(jgjj 
. bv appears certain, that this was a building in 
f '^ts of tK ™cans of pipes properly disposed, the va- 
the 0 ^ were introduced into different rooms, 
.^uiin.- .. bf patients. To these ruins, however, tlie 
ger extend ; so that, if this edifice had re- 
Ptifi 
Hi 
“«rs 
"ted 
•to Ion 
H 
^Vl . '—XLV-liVA y SW LUUt^ lA 111L9 AJMia » W 
?ose foy j f*- could not have been employed for the 
ich 
."'It'ch it was intended. The veins of pyrites 
.y more ancient conflagrations of the 
Plaroo es and Curaa, and which, 
entirelv consumed, annrnach their total 
Hi®ct 
entirely consumed, approach their total 
proceed to the experiments within the 
•he ■'"•‘phi tic '"'•'s f° determine die height of 
Of -''"crsectiQ' "Pbb'’ centre of the grotto, that is, at 
^iffs ^bates/K°^ ••* greatest length with thfit 
•h(i iHt .j'.cadth. This lieight varies according to the 
He ''^•‘sity •’••d temperatures of the atmosphere, 
^*1>Q in 3nd the accidental variations which 
*"^n'^‘®Pvodu' '? internal fermentadons by which the 
f. ’ "t hearbr • ■ •"•‘'•y> however, be estimated, at a 
Lt inches. 
" ®nteri,]„ • experiments regarded the degree of 
5 mto the mephitis : it was slightly sensible 
