296 Profefar Wit. L11AMS on Earthguakes. 
that what moved under, and hove up the furface of the earth, 
was a ftroug elajiic vapour.* 
The origin or production of fuch a vapour, may be accounted 
for from the cox TEN Ts of the earth. Much the largeft part 
of the contents of the earth, will always remain hidden from 
-our view, and beyond the reach of our knowledge. We have, 
however, penetrated far enough below its furface to find, that 
many of the bodies it contains, are of fuch a texture, or con- 
tain particles of fuch a nature, as to generate, or be eafily turn- 
ed into vapour. This is the cafe with coals, falts, fulphur, 
nitre, air, water, mof- kind of minerals, and all fubftances 
which contain oily particles. Such bodies, at leaft fome of the 
particles they contain, are æafily and often turned into a very 
ftrong, fubtle, elaftic vapour. With fome, nothing more is 
neceflary to generate a very powerful vapour, than a bare mix- 
ture of different bodies. Thus equal quantities of powdered 
fulphur and iron filings, being mixed with water, foon become 
too hot to be touched ; and in a little time emit flame and va- 
pour. And if iron, oil of vitriol, and water, become mixed 
together, there will inftantly arife a violent ebullition, with 
fumes copioufly exhaling ; and which are fo very inflammable, 
that if {et on fire, they go off at once with a loud explofion. 
‘The fame is alfo effected by fermentation. Inftances of very 
{trong elaftic vapours, produced this way, are fo common and 
obvious, that particular cafes need not be mentioned. All fe- 
.. parable, mixt and compound bodies, may be the fubje& of this 
_ soperation : and the eafier they are Íeparable, whether by means 
; = * ‘of 
bes From the phenomena which have been mentioned, it feems probable, that 
this elaftic vapour was 2 fluid, of the fame nature as that which is now called iz- 
Jammall: air, 
