[ 610 ] 
communication between the water and fire would be 
brought on, and that by degrees only. Hence the 
vapour, not being produced at once but gradually, 
might creep * filently between the ftrata, towards 
that quarter where the fuperincumbent mat's of earth 
was lighted: ; and, by this means, fome places very 
near the fource of the vapour might be little, or not 
at all, aftedted by it, whilft others might be greatly 
aftedted, though they lay at a great diftance ; and 
even thofe places, which lay immediately over the 
part where the vapour was pafting, might not per- 
ceive any effedt, on account of the gentlenefs of the 
motion, occafioned by the finall quantity of it. This 
might continue to be the cafe, till it came to fome 
country where, the fet of ftrata above being much 
thinner, the vapour would not only be hurried for- 
ward, but collected alfo into a much narrower com- 
pafs; and therefore, raifing the earth more, would 
produce more fenfible effedts j and this we ought 
* Some appearances that have been obferved in New England 
feem to confirm this, and make it probable, that a fmall quantity 
of vapour is often found to creep filently between the ftrata, before 
a general communication between the water and the fire gives rife 
to the greater and more fenfible efFedts of earthquakes. See Fhilof. 
Tran f. N° 462. or Martyn’s Abr. vol. viii. p. 693. where we are 
told, that, at Newbury, a little before any noife or fhock was per- 
ceived, the bricks of an hearth were obferved to rife, and, falling 
down again, to lean another way. In the fame account, it is alfo 
faid, that “ a few minutes before any fhock came, many people 
“ could foretell it by an alteration in their ftomachs:” an effect, 
which feems to be of the fame kind with fea-ficknefs, and which 
always accompanies the wave-like motion of earthquakes, when it 
is fo weak, as to be uncertainly diftinguifhable. 
chiefly 
