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ME. EOBEET MALLET ON VOLCANIC ENEEGY. 
Appendix. 
A. Thermal Springs. 
Authors on Yulcanology generally view thermal springs as one of the manifestations 
of volcanic action. That they are, in many instances, connected with volcanic vents, 
whose energies are nearly or for a time exhausted, is evident from such instances as the 
great hot springs of Auvergne or of Iceland ; hut that they are not related directly to 
volcanic agency in the vast majority of instances is equally obvious. In no case can we 
consider the surface-waters of supply descending many miles under ground ; so that 
thermal waters, such as those of the British Islands and of a large portion of Europe, 
cannot be viewed as manifestations of volcanic activity, hut as due to the surface-waters 
descending a certain moderate depth (which cannot be great, as no absolutely boiling 
spring is known except close to volcanoes), getting heated by the warmer beds below 
and reascending. We must therefore view the vast majority of the thermal springs of 
the globe in the light, not of volcanic phenomena at all, but as simply one of the means 
by which hypogeal heat is carried to the surface to be dissipated by radiation. It 
becomes an interesting inquiry in relation to our subject to estimate whether in this 
aspect the influence of thermal springs is great, or what proportion of the total heat 
lost annually by our globe is thus brought to the surface. 
The writer has attempted this estimate in the following way : — 
The thermal springs of Europe are those best known ; next to these, perhaps, may be 
viewed those of India as catalogued by the Messrs. Schlagentiiweit. Adopting 
Dr. Daubeny’s catalogue (‘ Volcanoes,’ See.) for the former, there are in Europe 154 hot 
springs scattered over an area of 34 millions of square miles, evolving 6577353752 
cubic feet of water per annum at a mean temperature of 57° Fahr. above the mean 
annual temperature of the localities. In India (as comprehended in the above 
catalogue) there are about 100 hot springs scattered over an area of 1^ million of 
square miles, evolving 4345000000 cubic feet of water per annum at a mean tempera- 
ture of 51°Eahr. above the mean annual temperature (taken for all India as 75° Fahr.). 
These together, therefore, distributed over an area of 5 millions of square miles (of 
tropical and temperate latitudes) evolve about 10862353752 cubic feet of water per 
annum at a general mean (quantity and temperature both taken into account) of 
54°-6 Fahr. 
If, now, we assume that all the remainder of the dry land of our globe present like 
thermal springs in like abundance, then the total evolution annually from the 52 
millions of square miles of dry land is 112968337520 cubic feet at 54 0, 6 Fahr. above 
the mean temperature of the localities. That is equivalent to 34336880705 cubic feet 
of water raised from 32° to 212° Fahr., or to 0’2332 cubic mile of water boiling under 
1 atmosphere brought to the surface per annum. 
If, now, from the insufficient character of our data, and especially as respects South 
America and Africa, we suppose that the above estimate does not comprise more than 
