C 601 ] 
doth in a wave all the way as it goes. In like man- 
ner, a large quantity of vapour may be conceived to 
raife the earth in a wave, as it paffes along between the 
ftrata, which it may eafily feparate in an horizontal 
direction, there being, as I have faid before, little or 
no cohefion between one ftratum and another. The 
part of the earth that is firft railed, being bent from 
its natural form, will endeavour to reftore itfelf by 
its elafticity, and the parts next to it beginning to 
have their weight fupported by the vapour, which 
will infinuate itfelf under them, will be raifed in their 
turn, till it either finds fome vent, or is again con- 
denfed by the cold into water, and by. that means 
prevented from proceeding any farther. 
59. If a large quantity of vapour fhould continue 
to be generated for fome time, feveral waves might 
be produced' by it; and this would be, in fome mea- 
fure, the cafe, if the quantity at firft generated was 
exceedingly great, though the whole of it was gene- 
rated in lefs time, than whilft the motion was propa- 
gated through the diftance between two waves. 
60. Thefe waves mufit rife the higher, the nearer 
they are to the place from whence they have their 
fource ; but, at great diftances from thence, they 
may rife fo little, and fo flowly, as not to be per- 
ceived, but by the motions of waters, hanging branches 
in churches, &c. 
61. The vibratory motion occafioned by the firft 
impulfe of the vapour, will be propagated through 
the folid parts of the earth, and therefore, it will 
much fooner become too weak to be perceived, than 
the wave-like motion ; for this latter, being occa- 
fioned by the vapour infinuating itfelf between the 
ftrata, . 
