Natural History of Volcanos and Earthquakes. 249 
toa state of rest, or at least until it-receives a fresh supply of lava 
_ from adistance. If the afflux of water be not interrupted, the 
__ exhalations of vapor may still continue, of which we have already 
mentioned several instances. 
| We may next consider how lava may be elevated from the 
| depth of a volcanic focus. 'The hypothesis, which ascribes vol- 
canic phenomena to the central heat, supposes that melted matters 
exist at a certain depth. In adopting this opinion, we need not 
asstme that lava is produced by the melting of solid rocks, but 
on the contrary, that melted matters have existed since the crea- 
tion of the world.* In the annexed diagram AB represents the 
s 
boundary between the solid crust of the earth and the melted 
; ‘Matters in the interior of the earth ; CD represents a wide rent, 
exhibiting a communication from the surface to the melted mat- 
_ tes; EF, GH, IK, LM, &c., are narrow rents conducting water 
: from the sea or subterranean collection of water to the heated in- 
_ letior ;+ and F, H, K, M, may be caverns in the solid crust, 
formed during the consolidation of the originally fluid matters of 
@ former period. Under these circumstances it may easily be 
Conceived, that water penetrating into the above mentioned rents 
and caverns is converted into steam, which, by pressing on the 
Melted matters, causes them to rise through the rent CD. If the 
lower opening in the wide rent at D be on the same level as the 
Whole boundary between the solid rocks and the melted matters, 
cacao ee eee ence 
é On this supposition, we assume that no basalt has been produced by the repeated 
melting of any known rock. Leonhard’s Basalt Gebilde, &c. Stuttgart, 1832, 
“1, p. 263. 
7 : t Water will naturally also penetrate into the wide rent, but, inasmuch as it is 
7 Xt able to fill up the rent, it cannot confine the steam generated beneath, and the 
will therefore escape 
Vol. Xxxvi, No. 2.—April-July, 1839. a 
