ll6 
SUBTEnRANEOUS WONDERS. 
vapour of this grotto, from a persuasiou that they j|f 
tend to tlirow a new light on physiology and natural 
sophy. Being, however, prevented from undertaking A 
by his duties as a professor, his friend, the Abb6 Bre' ^ 
who resided near the spot, engaged in the task ; an ^ 
following is an abstract of his learned memoir on 
subject. i,iP 
It is well known, the Abbe observes, that the niopj^ 
vapour occupies the floor of a small grotto near th® j|; 
Agnano, a place highly interesting to naturalists fron' 
phenomena its environs present, and the hills within ' ^ 
it is included. This grotto is situated on the south-ca*^^ 
of llie lake, at a little distance from it. Its length it* 
- - leaP. 
twelve feet, and its breadth from four to five. It apP^^ 
have been origiDall}'’ a small e.xcavation, made for the Pj!^t 
of obtaining puzzolana, an earth which, being apP'h |t( 
mortar, becomes a powerful cement. In the sides o*^ 
grotto, among the earthy volcanic matters, are found P^^.jil 
of lava, of the same kind with those which are ron’- 
scattered near the lake. 
The Abbe is persuaded that, if new excavations 
'v *- # 
be made in the vicinity of the grotto, at a level 
floor, or a little lower, the same mephitic vapour' ^ 
be found ; and thinks it would be curious to ascert**^^ i 
limits of its extent. It would also be advantage^’^^^.p 
physical observations, if Ore grotto were to be son'S^ 
enlarged, and its floor reduced to a level horizontal F 
by sinking it two or three feet, and surrounding it bf^ ji* 
wall, with steps at tlie entrance. In its present 
extremely inconvenient for experiments, and the ilj 
of the ground towards the door causes a great part 
vapour, from the effect of its specific gravity, to 
way out close to the ground. 
When the narrow limits of this place are considei^^';.* 
ca'‘; 
the small quantity of tlie vapour which has rendera^ ^ 
celebrated, there cannot be any doubt but that it 
dergone considerable changes ; since it does not 
probable that Pliny refers to the present confined 
only, when, in enumerating many places from ^ 
deadly air exhaled, he mentions the teiTitory of i . p’ 
The internal fermentations by which it is caused 
tainly much diminished in the vicinity of the lake 
