[ 6i8 3 
that the ftrata over it were of great thicknefs, as ap- 
pears from the great velocity with which the earth- 
quake was propagated there: the fhocks alfo con- 
tinued with equal, or nearly equal violence, for fome 
months after the openings were made j whereas, if 
thefe fires had been the caufe of them, they mult 
immediately have ceafed, upon the fires finding 
a vent, as it has happened in other * cafes. It is 
therefore much more probable, that a very large 
quantity of vapour, taking its rife from fome far 
more extenfive fire under the fea, fpread itfelf from 
thence; and as it pafted in places, where the roof 
over it was naturally much thinner, as well as greatly 
weakened by the undermining of thefe fires, it opened 
itfelf a paftage, and bur ft forth. 
80. As the moft extenfive earthquakes generally 
proceed from the loweft countries, but efpeciallv 
from the fea, fo thofe of a fmaller extent are gene- 
rally found amongft the mountains: hence it almoft 
always happens, that earthquakes, which are felt near 
the fea, if at all violent, are felt alfo in the higher 
lands; whereas there are many amongft the hills, 
and thofe very violent ones, which never extend 
themfelves to the lower countries. Thus we are 
told, that, at Jamaica, “ •f* {hakes often happen in 
“ the country, not felt at Port-Royal ; and fome- 
<c times are felt by thofe that live in and at the foot 
* See art. 28. 
t This is taken from an account of the earthquake that hap- 
pened at Jamaica in the year 1692, which, as well as fome others 
before- mentioned, was attended with the wave and previous re- 
treat. See Philof. Tranf. N° 209. or Lowthorp’s Abr. vol. ii. 
p. 417 and 418. 
“ of 
