ON THE FACTS OF EARTHQUAKE ΡΗΖΝΟΜΕΝΑ. 27 
_ But conversely, not only are eruptions thus accompanied by earthquakes, 
but earthquakes, though not always, are on almost all great occasions accom- 
panied by eruptions or perturbations of established volcanic action, For ex- 
ample, during the great Calabrian earthquake Stromboli was noticed to be 
less active than it had been for years before, and at Messina, “the com- 
mandant of the citadel saw the sea at a quarter of a mile from the fortress 
rise up and boil in a most extraordinary manner, accompanied with a horrid 
noise, while all the rest of the water in the Faro was tranquil” (Sir W. 
Hamilton); and afterwards there was shoal water at the spot where before 
it had been deep. 
In the great Chilian earthquake of 1820, at the moment the shock was 
felt at Valdivia, in lat. 39° 50’ S., two volcanoes near it burst at once into 
eruption for a few seconds, and then again became quiescent. (M. Place, 
Quart. Journ. vol. xvii.) 
At Concepcion, volcanoes broke out from beneath the sea at the time the 
great sea-wave rolled in (or probably before it ?). 
Hot springs have frequently sympathized with earthquakes at great di- 
᾿ς Stances, as those at Toepliz, which ran dry, and then again flowed discoloured 
| _ with iron rust during the great Lisbon shocks. No one is ignorant of the 
| melting of the chain cable of the Volage man-of-war at anchor during an 
earthquake off the coast of South America; and instances might be multi- 
plied almost without limit of similar events during the period of earthquakes 
_ which have not been begun with visible eruptions from neighbouring vents. 
ea ; _ Thus the close connection of volcanic action and of earthquake movements 
τς must be viewed as abundantly established. 
___. There appear to be over the earth’s surface at least twenty eruptions per 
annum, and probably quite as many considerable earthquakes. Several in- 
stances are on record of earthquakes haying at once ceased on the opening 
up of yoleanie vents near or more distant, Thus Strabo (lib. i. p, 85) re- 
lates, that the shocks of the island of Eubcea ceased as soon as a crevasse 
formed in the Lelantine plain, which discharged “a river of fiery mud,” ὁ, ὁ. 
_ of lava. That such vents are efficient at enormous distances from the shaken 
country is well evidenced; it is only, in other words, that earthquake shocks 
are transmitted from their centres to vast distances. 
There are not data to enable us now to affirm what portions of the earth’s 
surface are now or have been at given epochs least affected by earthquakes, 
hor does it follow that those most remote from volcanic active centres will 
be those least subject to éarthquakes; on the contrary, there is reason to 
% Ayppose that the intervening formations, in the nature and depth of their 
_ rocks or loose materials, have much influence upon this. It is certain that 
7th. Many portions of the earth’s surface, which are not now 
active volcanic centres, nor very closely adjacent thereto, nor 
yet the centres of extinct volcanic action, are subject to fre- 
quent earthquakes. 
Thus earthquake shocks have been felt even in the loosest alluvial depo- 
sits of Holland, around Middleburg and Flushing, in the great Prussian 
plain, and at Cutch, in the low-lying Delta of the Indus. 
8th. Regions which are the centres now of extinct volcanic ac- 
tion do not appear more subject to earthquakes than other 
regions whose formations are altogether non-volcanic. 
9th. Although regions of active volcanic action are those also of 
most frequent earthquake movements, yet the most violent 
