Natural History of Volcanos and Earthquakes. 249 



to a state of rest, or at least until it receives a fresh supply of lava 

 from a distance. 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 

 assume 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 



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- 

 ters ; EF, GH, IK, LM, &c., are narrow rents conducting water 

 from the sea or subterranean collection of water to the heated in- 

 terior ;f and F, H, K, M, may be caverns in the solid crust, 

 formed during the consolidation of the originally fluid matters of 

 a 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, 



* On lliis supposition, we assume that no basalt has been produced by the repeated 

 melting of any known rock. Leonliard's Basalt Gebilde, &c. Stuttgart, 1832, 

 t. i, p. 263. 



t Water will naturally also penetrate into the wide rent, but, inasmuch as it is 

 not able to fill up the rent, it cannot confine the steam generated beneath, and the 

 latter will therefore escape. 



Vol. XXXVI, No. 2.— April-July, 1839. 32 



