101 
rtlltlCE-STOMSS 01 Tilts peak. 
tho earthquakes preceding eruptions. Without adopting an 
opinion, which seems somewhat bold, I made, in concert with 
M Larea, a senes of experiments on the tumefaction of the 
lolcamc vitreous substances at Teneriffe, and on those which 
are found at Quinche, m the kingdom of Quito. To judge 
of the augmentation of their bulk, we measured pieces 
posed to a forge-fin of moderate heat, by the water they 
I- Cylu i dnc S lass > enveloping the spongy mass 
with a thin coating of wax. According to our experiments, 
t \ ety une W alJ T : tl 'ose of the Peak and 
the black rarities of Cotopaxi and of Quinche increased nearly 
hve tunes their bulk. • 
The colour of the pumice-stones of the Peak leads to 
another important observation. The sea of. white ashes 
v nch encircles the Piton, and covers the vast plain of 
ri er’ •“ TT* 1 '. ^ of the *>™er activity^ the 
crater : for m all volcanoes, even when there are lateral 
erupt. ons, the ashes and the rapilli issue conjointly with The 
vapours only from the opening at the summit of the mourn 
taui. W at Tencrifie, the black rapilli extend from tho 
loot of the Peak to the sea-shore ; while the white ashes 
Mich are only pumice ground to powder, and among which 
an In TT 0 ' ° ’ l " 1 ! 1 !, j lclls ’ fragments of vitreous feldspar 
PcW 1 Thi’ 0 ’ the re 8 i01 i "ext to the 
leak. This peculiar distribution seems to confirm the 
observations made long ago at Vesuvius, that the white 
ashes arc thrown out last, and indicate the end of the erup- 
tion. In proportion as the elasticity of the vapours di.ni- 
Jitslies, the matter is thrown to a less distance; and the 
black rapilli, winch issue first, when the lava has ceased 
1 T? llm ' ssaril J reach farther than the white ra- 
of .a morelntense l "'° loen "'"”1 *“ «“ “‘ion 
4 tesssttu sas sm ass 
«8'»” ° «» to tho top of tL fin “l ' ro e ! 
deavoured to render these research,:.. i„tere,ti„„ 
paring the phenomena of the volcano of TeneriH'e°with those 
that are observed in other regions, the soil of which is equally 
SUbtei T a i 1 ! ea, ‘ , fIres ' This mode of viewing 
Nature m the universality of her relations is no doubt J. 
