Geology and Natural History, 223 
volcanic vents. 2. The evolution of steam and other heated 
elastic fluids by which these are carried. 3. The work of raising 
h : 
of the source I have assigned for volcanic heat, in ways, Viz: 
1. To the phenomena presented during the last two thousand 
years by Vesuvius, the wn volcano in the world; and 
have ever been known in activity. 
It is impossible here to refer to the details of the method or 
Steps of these calculations. The result, however, is, that making 
large allowances for presumably defective data, less than one- 
Sourth of the total telluric heat annually dissipated (as already 
stated in amount) is sufficient to account for the annual volcanic 
Position transitorily of material within or upon our g obe, the 
Proportion of the mass of which to the whole is equally insignifi- 
cant, so not likely in any way to produce changes recognizable by 
the astronome 
melted mass, for the production, through the contraction ot its 
volume, of all the phenomena of elevation and of vulcanicity 
s. dh 
Well as basalts, present in chemical and physical constitution close 
resemblance, an may be all referred to the meltin of more or 
less fusible mixtures of siliceous erystalloid rocks yi al pi ~ 
(slates, ete.) and calcareous roc Their general chemical 
