242 “Natural History of Volcanos and Earthquakes. 
Paris inches of a column of mercury from this formula, we shall 
have log. e=2 8316686 + log. (213+1)— ot 
in which ¢ is the temperature in degrees of Reaumur = 
- Pe 
It is clear that the elastic force of steam cannot surpass a cer- 
tain maximum, which it reaches when its density is equal to 
that of water. This is the case when the elasticity of the vapor 
€=232952 Paris inches of mercury, or nearly 8320 atmospheres, 
which supposes a temperature of 2786° F.t 
Thus, if aqueous vapor were to reach its greatest possible elas- 
ticity, its temperature must exceed that above assumed for the 
melting point of lava by 504° F. The highest column of lava, 
which steam at its maximum elasticity is capable of supporting, 
is, therefore, if we suppose the specific gravity of liquid lava three 
times as great as that of water, 88747 feet. But a temperature 
of 2786° F. will, according to the observations at Geneva and in 
Cornwall, be met with at a depth of 139265 feet, and according 
to those in the Frzgebirge, at a depth of 155613 feet (about 
thirty English miles) below the level of the sea near Vesuvius 
or Hina.t 
Supposing, then, the values found for the maximum elasticity 
of steam for the corresponding temperature, and for the depth at 
which that temperature must exist, to be correct, it would not be 
possible, that a column of lava, of the whole height, from the seat 
of the volcanos to the surface of the earth, should be raised Up: 
On the other hand, in the same manner as a bubble of air let into 
a barometer, dives the mercury into the Torricellian vacuum far 
above the barometric height, aqueous vapor may raise a column 
of lava of a height equal to its expansive force into the chand 
opening into the craters. Thus, then, it may happen that aqueous 
vapor, though far from its maximum elasticity, may yet be able 
to raise a column of Java equal in height to its elasticity from still 
greater depths to the surface of the earth. A continual alterna- 
tion of columns of Java and steam in the channels may be Very 
well conceived, the consequence of which would be an alternate 
a 
On steam and steam engines in the Abhandlungen der Kénigl. technische® 
Deputation far Gewerbe, part i, p. ¢ t Ibid. 
Supposing the mean temperature of this localtiy = 61° F. 
eae 
Tans we 
