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such as the rise in the temperature of the hot springs of the 
island, &c. 
If most so-called earthquakes are but accidental sinkings of the 
surface, how are we to account for all the variety of circumstances 
usually accompanying them, the different motions so clearly felt 
and tested by instruments? The volcanic eruptions, the atmos- 
pheric disturbance which though not, I admit, universal, in most 
cases either precede or follow the disturbance. I confess I am 
unable to do so; and I think we may dismiss this idea, and turn 
to the more generally entertained theory of electro-magnetic 
currents. I cannot doubt for a moment that electricity plays a 
very important part in these terrible manifestations, that even 
the solid earth may be at times as treacherous as the ocean ; but 
I do consider that unaided by the explosive power, chiefly of 
steam, but possibly of other vapours and gases besides, electricity 
alone would not produce those mighty dynamic effects with which 
the world is but too familiar. Electric currents passing obstacles 
in the shape of non-conductors, would undoubtedly produce 
shocks and jars; but though on a gigantic scale, it would be 
natural to suppose that these would partake of the nature of those 
given by a battery ; and the heaving and rocking of the ground 
must directly be the work of confined vapours, suddenly expanded 
by intense heat. In ordinary cases, where no actual splitting of 
the surface occurs, may we not assume that these natural 
torpedoes expend their force in bursting from one subterranean 
chamber to another; but that in the more serious ones such a 
vent being closed to them, they break out wherever the crust 
above them is weakest? There is apparently a great example of 
this in the recent catastrophe at Java. 
It has been remarked that most serious cases of earthquake 
have not, as a rule, taken place in the neighbourhood of volcanoes : 
Humboldt at once explains this when he says :—“ Active 
voleanoes may be regarded as safety-valves for the country in 
their immediate vicinity.” And this idea seems fully borne out 
