upon the Phenomena, of Earthquakes. 335 
great shakes continued, bellowed out prodigious loud noises and 
echoings. 
87. ‘Not far from Yallowes, a mountain, after having made 
several moves, overwhelmed a whole family, and a great part of 
a plantation, lying a mile off; and a large high mountain near 
Portmorant, near a day’s journey over, is said to be quite swal- 
lowed yp. 
58. ** In the blue mountains, from whence came those dread- 
ful roarings, may reasonably be supposed to be many strange al- 
terations of the like nature; but those wild desert places being very 
rarely, or never visited by any body, we are yet ignorant of what 
happened there; but whereas they used to afford a fine green 
prospect, now one half part of them, at least, seem to be wholly 
deprived of their natural verdure*.” 
Section VI.—89. I have supposed, that fires lying at the 
greatest depths generally produce the most extensive earthquakes. 
We must, however, except from this rule those cases where the 
depths are very great: for, as the weight of three miles perpen- 
dicular of common earth is capable of absolutely repressing the 
vapour of inflamed gunpowder, so we may well suppose, that 
there may be a quantity of earth sufficient to repress the vapour 
of water, and keep it within its original limits, though ever so 
much heated. Now, whenever this is the case, it is manifest, 
that it can produce no effect: or, it may happen, that though 
the quantity of earth may not be sufficient absolutely to repress 
the vapour, yet it may be so great, as to suffer it to expand but 
very little: in this case, an earthquake arising from it would he 
but of small extent; the wave-like motion would be little or none; 
the vibratory motion would be felt every where ; and the propa- 
gation of the motion would be very quick. This last circumstance 
being almost the only one, by which these earthquakes can be 
known from those which owe their origin to shallower fires, it 
must be very difficult to distinguish them with certainty, as it is 
almost impossible to distinguish the difference of the time of their 
happening in different places, when the whole, perhaps, is com- 
* See Philos. Trans. No. 209; or Lowthorp’s Abridg. vol. ii. p. 416, &c. 
where there is a great deal more to the same purpose. See also Hist. and 
Philos. of Earthq. p. 286 and 287. 
From the authorities quoted in this section, it appears, how little reason 
there is for the notion, that either large cities, or towns situated near the 
sea-coast, are more subject to violent earthquakes than others: it is not, 
however, much to be wondered at, that such a notion should have prevailed, 
after the great destruction that happened in so large and populous a city as 
Lisbon; since the demolition of a few ruinous houses only, in such a place, 
would have affected the imaginations of men more, and would have been 
more taiked of, than the subversion of whole mountains in some wild and 
desert country, where at most half a dozen unknown shepherds might feel 
the effects of it, or perhaps only see it at a distance. 
prehended 
