MODIFIED ly COMPRESSION. 169 
upwards. That they have been really fo propelled, from a 
great internal mafs of matter, in liquid fufion, feems to admit 
of no doubt, to whatever caufe we afcribe the heat of volcanoes. 
It is no lefs obvious, that the temperature of that liquid mutt 
be of far greater intenfity than the lavas, flowing from it, can re- 
tain when they reach the furface. Independently of any actual 
eruption, the body of heat contained in this vaft mafs of liquid, 
mutt diffufe itfelf through the furrounding fubftances, the in- 
tenfity of the heat being diminifhed by flow gradations, in pro- 
portion to the diftance to which it penetrates. When, by means 
of this progreffive diffufion, the heat has reached an affemblage 
of loofe marine depofites, fubject to the preflure of a great fu- 
perincumbent weight, the whole muft be agglutinated into a 
mafs, the folidity of which will vary with the chemical com- 
pofition of the fubftance, and with the degree of heat to which 
each particular fpot has thus been expofed. At the fame time, 
analogy leads us to fuppofe, that this deep and extenfive heat 
muft be fubjec to viciflitudes and intermiflions, like the exter- 
nal phenomena of volcanoes. We have endeavoured to explain 
fome of thefe irregularities, and a fimilar reafoning may be ex- 
tended to the prefent cafe. Having fhewn, that fmall in- 
ternal {treams of lava tend fucceflively to pervade every weak 
part of a volcanic mountain, we are led to conceive, that the 
great mafles of heated matter juft mentioned, will be fucceffive- 
ly dire&ed to different parts of the earth; fo that every loofe 
affemblage of matter, lying in a fubmarine and fubterranean 
fituation, will, in its turn, be affected by the indurating caufe ; 
and the influence of internal volcanic heat will thus be cir- 
‘cumfcribed within no limits but thofe of the globe itfelf. 
A sERIES of undoubted facts prove, that all our ftrata once 
Jay ina fituation fimilar in all refpeés to that in which the 
_ marine depofites juft mentioned have been fuppofed to lie. 
Tue inhabitant of an unbroken plain, or of a country form: 
ed of horizontal ftrata, whofe obfervations have been confi- 
Von, VL—P. I. Y ned 
