into the Crater of Mou nt Vesuvius . 17 
different volcanic matters which appeared to be new or 
curious, and endeavoured to make a few observations. 
Had we been allowed to depend on success, bad we 
not been retarded in our preparations by our timid guides, 
&nd if some of us, having only just arrived at Naples, 
had not been straitened in point of time, our descent would 
certainly have been much more useful, and the results 
more satisfactory. However, though ill furnished with 
means, the following are the observations we were ena- 
bled to make : 
Heaumur ? s thermometer, the only instrument we pos- 
sessed, stood at i2 degrees, on the summit of Vesuvius: 
the air was cold, and somewhat moist : in the crater the 
quicksilver rose to 16 degrees, and we experienced the 
mildest temperature. 
The surface of this place, which, when seen by the 
naked eye, looking down from above, appeared entire- 
ly smooth, exhibited, when we were at the bottom, no- 
thing but a vast extent of asperities. We were constant- 
ly obliged to pass over lava exceedingly porous, in ge- 
neral pretty hard, but which in some places, and particu- 
larly those where we entered, was still soft, and yielded 
under our feet. The spectacle which struck us most was 
the numerous spiracles, which, either at the bottom of the 
crater or the interior sides of the mountain, suffer the va- 
pours to escape. When we arrived at the crater, we 
were desirous to ascertain whether these vapours were 
of a noxious quality : we walked through them, and in 
spired them several times, but felt no inconvenience from 
them. The thermometer placed in one of these spira- 
cles indicated 54 degrees, in another it rose only to 22. 
In all these experiments our instrument was covered 
with a humid matter, which was soon dissipated in the 
open air without leaving any traces. 
Vol. it. c 
