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 j yet, on the other hand, we must consider, that when the 

 vapor, v/hich 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. For 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 an 

 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, on 

 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 Sca7i- 

 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 that 



