(ee eagle le 
eas 
Natural History of Volcanos and Earthquakes. 243 
ejection of lavas, red hot masses, and clouds of steam, just as 
Spallanzani,* Scrope,t and Hoffmann, observed on Stromboli. 
We have now to examine the circumstances under which wa- 
ter might find its way to the origin of volcanic action. The diffi- 
culties which present themselves when we suppose a direct com- 
munication between the sea and the seat of the volcanos, have 
already been discussed by Gay-Lussac. We shall make an at- 
tempt to solve these difficulties. 
If we imagine the sea to have free access by means of fissures 
to the seat of the volcanos, the depth of which, according to the 
above calculation, may be taken at from 113505 to 126829 feet, 
the elastic force of steam at that depth, where t=2282° F.., will 
be =5310 atmospheres. But the hydrostatic pressure of these 
columns of water is only from 3547 to 3963. atmospheres. The 
expansive force of steam at that depth in which the temperature 
is 2282° F, is, therefore, greater than the hydrostatic pressure 
opposed to it, so that the latter cannot resist it- But since, as 
the temperature decreases, this expansive power diminishes more 
‘apidly than the hydrostatic pressure, there must be a certain 
epth and a corresponding temperature in which they will be in 
equilibrium. For a constant increase of temperature of 1° F’. in 
51 feet, this point will be at the depth of 88044 feet below the 
Surface of the sea, where the temperature is 17549°.5 F. ;§ for, 
’€cording to the above formula, if ¢ be taken equal to 1754°.5, 
a lel as 
* Voyag. t. ii, p. 21. 
t Considerations on Voleanos, &c., p. 54. A phenomenon observed by 
during the night in the crater of Stromboli distinctly shows, that, by the force of 
aqueous vapor alone, the column of lava is raised. The lava once suddenly dis- 
r 
being discharged by the sinking lava which had become tenacious on the s 5 
will now escape laterally through the fissures in the walls of the edge of the cra- 
Abhan 
§ To simplify the calculation, I have supposed the mean temperature of the 
Surface — 32° F. 
