On Volcanos and Earthquakes. 17 



must penetrate, under ground at four miles and seven-eighths 

 below the surface of the earth, through the crevices of the 

 rocks, and in all the subterranean vacuities which communi- 

 cate with each other, or with the general reservoir of air. 

 And if it meets there, or rather, when it meets there com- 

 bustible substances, as bitumen, sulphur, coal, &c. a confla- 

 gration must ensue, which is constantly supplied with a new 

 quantity of blowing air, forced by the pressure of the sea, as 

 if by a permanent forge bellows. The air, after having sup- 

 ported combustion, rarefied by the heat, opens its way, and 

 issues by apertures at the summit of volcanic mountains, 

 which we have called craters, as it does in common chim- 

 nies at the top of the flues. Such is our conception of these 

 subterranean fires called volcanoes, considered in their quiet 

 and peaceful operation. 



It would be difficult to conceive how combustion should 

 be constantly supported under ground without a constant 

 supply of air ; and we do not perceive how that air would be 

 brought into those subterranean cavities, except by the 

 means just suggested ; we see no hole or opening which 

 might be considered as a draught for the passage of air ; on 

 the contrary, ail the apertures observed emit gases that may 

 be considered as the result of the conflagration of combusti- 

 ble bodies, and decomposition of water by fire. We see 

 smoke ascending from the top of volcanic mountains, and 

 all these phenomena seem to speak in favour of our hypoth- 

 esis. 



We do not think it necessary to enlarge on the various 

 products of these subterranean fires ; a great deal has been 

 said and pubhshed on this subject; the formation of carbo' 

 nic acid ; its emission in its natural gaseous state ; its combi- 

 nation with lime, magnesia, metallic oxides, &c, ; its abun- 

 dance in mineral waters ; the flowing of hot water springs^ 

 either simple or sulphurous ; the rushing out of hydrogen 

 gas, sulphuretted or carburetted : these results are the natu- 

 ral effects of these permanent fires, considered in their quiet 

 state. 



Now, it is time to present our readers with the complement 

 of the theory by the spectacle of an eruption. A largo vol- 

 cano may be considered as a whole coalery on fire, several 

 miles and perhaps several hundred miles in extent, five miles 

 under ground, that is to say, under the inferior level of the 

 sea water ; coals, bitumen, sulphur, &c. are constantly burn" 



Vol. XV.— No. K 3 



