82 Sir WILLIAM HAMILTON’S Account of 
pumice, and refembles it in every refpect except being of 
a darker colour. 
When the pores of the frefh folid lava were large and 
filled with pure vitrified matter, w r e found that matter 
fometimes blown into bubbles on its furface, I fuppofe, by 
the air which had been forced out at the time the lava con- 
tracted itfelf in cooling : thofe bubbles, being thin, 111 e wed 
that this volcanic glafs has the kind of tranfparency of 
our common glafs bottles, and is like them of a dirty 
yellow colour. I detached with a hammer fome large 
pieces of this kind of glafs as big as my fill, which ad- 
hered to, and was incorporated with, fome of the larger 
fragments of lava, and, though of the fame kind, from 
their thicknefs they appeared perfectly black, and were 
opaque. 
Another particularity is remarkable in the lava of 
this eruption : many detached pieces of it are in the fliape 
of a barley-corn or of a plumb-ftone, fmall at each end, 
and thick in the middle. We picked up feveral, and favv 
many more which were too heavy for us to carry off, for 
they muft have weighed more than fixty pounds; fome 
of the fmaller ones did not weigh an ounce. I fuppofe 
them to be drops from the liquid fountain of fire of 
the 8 th of Auguft, which might very naturally acquire 
fuch a form in their fall ; but the peafants in the neigh- 
bourhood 
