ME. EOBEET MALLET ON VOLCANIC ENEEGY. 
149 
Close to the volcanic vent the eruptive throes may produce earthquake-impulse before 
or after these have broken through the earth’s surface ; but we cannot phenomenally 
connect most earthquakes with volcanic action at all, inasmuch as there is, even in the 
very greatest, no local change of terrestrial surface-temperature. 
We can only refer them to a common origin, if we can discover and describe some 
play of cosmical mechanism set in motion by terrestrial heat, that shall be sufficient in 
energy to account for all the phenomena, that shall bear examination when brought 
into contact with each particular class of well-ascertained facts, either of volcanoes or 
of earthquakes or of mountain-chain elevation, that shall leave none of these facts 
inexplicable, and that shall so link itself on to cosmical physics generally as to be 
applicable to like phenomena in other planets than our own, or satellites, so far as we 
have facts ascertainable in relation to these. 
• 5. Within the limits of this paper it is impossible to enter upon any large discussion of 
the theories that have been advanced as to the nature and origin of volcanic activity and 
elevatory action ; a few remarks upon the notions commonly current on these subjects 
amongst geologists are necessary, however, to point out their more salient defects and 
to contrast the views about to be here advanced with those which are current. 
6. Volcanic theories have been always of two classes, the chemical and the mechanical. 
Omitting all earlier, Davy’s notion that volcanic heat was due to oxidation of the metals 
of the alkalies or earths by contact with water, supported by Daubeny and in part by 
De la Beche, is that which has mainly engaged attention. Had it not been for the 
splendour of Davy’s genius and the announcement of this view at the moment of his 
great discovery of the bases of the alkalies, it would probably never have had even a 
momentary acceptance. 
Davy himself abandoned it at a later period. When we remember that the mineral 
constituents in the rocks known in the earth’s crust do not contain on the average more 
than about 4 or 5 per cent, of the alkaline metals taken together, and compare the nature 
of the total ejecta of volcanic vents, more especially those of gas or vapour as ascertained 
by many labourers, amongst whom must be distinguished Daubeny himself, Abicil, 
Bunsen, St.-Claiee Deville, and Fouque, with such as must result from Davy’s hypo- 
thesis, we can only wonder that one so absolutely gratuitous should ever have had a 
moment’s acceptance. 
There is no other “ chemical theory ” to put in its place. All great or violent chemical 
energies, powerful as these must have been in past time, when the materials of our planet 
were in vapour and dissociated by high temperature, have long since been as a whole 
satisfied. 
7. As the thermal energy of the shrinking mass was dissipated, and it passed from 
vapour to liquid, and from that in chief part to solidity, the chemical energies of the 
sixty or more elements we know of became satisfied by combinations, the order and con- 
ditions of which chemistry may yet hope to trace, though it cannot do so at present*. 
* Sterry Hunt and Stoney have, however, made the attempt. 
