84 Mr. Matter on the Dynamics of Earthquakes. 
whose origin is inland; hence our theory shews that, in one respect at least, the 
common opinion is well founded, that all great earthquakes’ come from the sea ; 
for besides that the earthquake whose origin is inland has, probably, always a 
smaller original impulse, because the disruptive forces, of whatever sort, are less 
opposed on land than they are under the bed of the deep sea, the inland earth- 
quake always wants the desolating conclusion of the overwhelming great sea wave. 
The conditions, then, just enunciated are precisely what we find did actually occur 
in the great Calabrian earthquake. The centre of impulse was situated, accord- 
ing to Dolomieu, at the intersection of a line drawn from Cape Vaticano to Cape 
Colonna, with another drawn from Cape Suvero to Cape Stillo; it was, there- 
fore, in the heart of Calabria. No great sea wave followed this tremendous earth- 
quake on the Calabrian coasts, and yet the shock was powerful enough to pass 
under the sea, and destroy the city of Messina upon the opposite shore of 
Sicily. 
Here there was, however, considerable agitation of the sea, the surges of 
which swept over the mole of Messina; but this was produced, we are told by 
Dolomieu, by waves generated locally, by the fall of an enormous mountain mass, 
which was broken off, and precipitated by the shock into the sea in the immediate 
neighbourhood of that city. A similar occurrence is recorded by Captain Basil 
Hall, I believe, as having occurred during an earthquake on the coast of South 
America, where an enormous mass of rock was observed suddenly to split off, and 
fall into deep water, producing a swell that was propagated and felt very far 
out to sea. In making observations during or subsequent to earthquakes, there- 
fore, or in discussing their particular circumstances, with a view to discover the 
centre of original impulse, it will be necessary always carefully to ascertain whe- 
ther great sea waves, observed at any point of the coast, have arisen from this or 
other such accidental event, or have come normally from the centre of impulse. 
I proceed now to point out in what respects the theory of earthquake 
motion, which I have thus, I hope, been enabled to make intelligible, differs from 
all others previously brought forward, and to show how Michell’s, which in some 
points appears most to resemble it (although the likeness is but apparent) fails 
altogether. 
Michell’s views, as to the agencies of vast regions of subterraneous vapour, 
pent up in a state of high elastic compression, seem to have been derived from 
