[ S8 9 1 
matter out of doubt. And, as it frequently happens, 
that volcanos rage for a time, and then are quiet 
again for a number of years j fo we fee earthquakes 
alfo frequently repeated for fome fmall time, and 
then ceafing again for a long term, excepting, per- 
haps, now and then fome flight fhock. And this 
analogy between earthquakes, and the effects of vol- 
canos, is fo great, that I think it cannot but appear 
ftriking to any one, who will read the accounts of 
both, and compare them together. The raging of 
volcanos is not one continued and uniform effedt; 
but an effedt, that is repeated at unequal intervals, 
and with unequal degrees of force : thus, for in- 
ftance, we flhall have, perhaps, two or three blafts 
difcharged from a volcano, fucceeding one another 
at the interval of a few feconds only : fometimes the 
intervals are of a quarter of an hour, an hour, a day, or 
perhaps feveral days. And as thefe intervals are very- 
unequal, fo is the violence of the blafts alfo : fome- 
times ftones, &c. are thrown, by thefe blafts, to the 
diftance of fome miles ; at other times, perhaps, not 
to the diftance of a hundred yards. The fame dif- 
ference is obferved in the intervals and violence of 
the fhocks of earthquakes, which are repeated at 
fmall intervals for fome time. 
Sect. II. 
. The great frequency of earthquakes in the 
neighbourhood of burning mountains, is a ftrong 
argument of their proceeding from a caufe of the 
fame kind : and the analogy of feveral volcanos lying 
together in the fame tradt of country, as well as new 
ones breaking out in the neighbourhood of old ones, 
4 G 2 tends 
