280 Natural History of Volcanos and Earthquakes. 
on the weight of the solid mass, whether the vapor can effect its 
elevation, and by what elasticity. Although we must suppose 
that the elastic force of the vapor progressively increases, in pro- 
portion as the temperature of the surface of rock in contact with it 
rises ; yet, on the other hand, we must consider, that when the 
vapor, which had not yet attained its maximum of expansive 
force, has effected an elevation, then, a regressive effect, as re- 
gards duration of time, will ensue, because, by the elevation, the 
space which confined the vapor has become enlarged. Secondly, 
if the conducting power of the solid mass be greater than we have 
just assumed it to be, then the heat, which is communicated to 
the surface of contact by condensation of vapor, is as quickly dif- 
fused above, as it can be conveyed from the vapor below, and if 
the latter produce a continued elevation, the effect must inevita- 
bly be regressive. We can therefore conceive it possible, under 
the conditions stated, that the same force, viz. vapor of water, 
which, when in contact with a fused mass, developes its whole 
intensity in a short time, can produce only a gradual effect, when 
in contact with solid masses whose temperature is far below that 
of the vapor. We thus see the possibility of fused masses being 
raised by vapor in a short time, while solid masses may be raised 
very slowly by the same agent, and that the latter elevation may 
go on in a regressive ratio. Lastly, it is even possible that a grad- | 
ual elevation of a solid mass may continue, although the elevating | 
effect of the vapor has long ceased. Fr instance, if the subter- 
raneous heating by steam continue, and if the heat, communica- | 
ted to the surface of contact by condensation of the vapor, be | 
diffused above more slowly than it is conveyed below, then it is 
clear that the solid mass, supported by the vapor, will gradually 
be expanded. | 
These remarks have shown that the operations of vapor, aS 2 
elevating force, may be very various as regards the relations of 
time and space, and that its effects depend not only on its own | 
temperature, but also on that of the masses it has to elevate, 0? | 
their relative conducting power, and lastly, on the capacity of the | 
space within which its operations take place. 
We can therefore understand how the slow elevation of Sean- 
dinavia may be the result of the operation of watery vapor, taking 
place in a diminishing ratio, and how therefore this phenomenon 
stands in close connexion with the original elevation of tha 
