264 Conjectures concerning the Cause, and Observations 
&c. to some miles distance: great stones also, of some tons 
weight, are often thrown to the distance of two or three miles by 
these explosions: and Mons. Bouguer tells us, that he met with 
stones in South America, of eight or nine feet diameter, that had 
been thrown from the volcano Cotopaxi, by one of these blasts, 
to the distance of more than three leagues *. 
54. If we suppose that these vapours, when pent up, are the 
cause of earthquakes, we must naturally expect, from what has 
been just said, that the most extensive earthquakes should take 
their rise from the level and low countries ; but more especially 
from the sea, which is nothing else than waters covering such 
countries. Accordingly we find, that the great earthquake of 
the Ist of November 1755, which was felt at places near three 
thousand miles distant from each other, took its rise from under 
the sea; this is manifest, from that wave which accompanied it, 
as shall be shown hereafter. The same thing is to be under- 
stood of the earthquake that destroyed Lima in the year 1746, 
which, it has been said, was felt as far as Jamaica; and, as it 
was more violent than the Lisbon earthquake, so, if this be true, 
it must, in all probability, have been more extensive also. There 
have been many other very extensive earthquakes in South Ame- 
rica: Acosta says, that they have been often known to extend 
themselves one, two, or three hundred, and some even five hun- 
dred leagues, along the coast. These have been generally, if 
not always, attended with waves from the sea; but any minuter 
circumstances accompanying them are not related. Indeed it is 
hardly to be expected that they should be observed, much less 
that they should be related, when they happened in a country 
so thinly inhabited, and where one may reasonably suppose, that, 
in general, only the grosser and more violent effects would be 
taken notice of. 
Section II].—55. I have said before, that I imagined earth- 
quakes were caused by vapours raised from waters suddenly let 
out upon subterraneous fires. It is not easy to find any other 
cause capable of producing such sudden and violent effects, or 
of raising such an amazing quantity of vapour in so small a time. 
That the blasts, discharged from volcanos, are always produced 
from this cause, is highly probable ; that they are often so, can- 
not admit of the least doubt. There can be no doubt, that con- 
siderable quantities of water must be often let out upon the fires 
* See Hist. and Philos. of Earthq. p. 195. Don Antonio d’Ulloa, an au- 
thor of great veracity, speaking of the same thing, says, that “the whole 
plain [near Latacunga| is full of large pieces of rocks, some of them thrown 
trom the volcano Cotopaxi, by one of its eruptions, to the distance of five 
leagues.” See his Voyage to Peru, part i. book vi. chap. 1. : 
+e) 
