210 On Earthquakes—their causes and effects. 
generally seen in connexion with an eruption of the vol- 
eano, but it is called into action by the unusual excitement 
of heat, and is therefore an effect and not a cause. Dolo- 
mieu denies the agency of electricity; he says, “ J’exclue 
Pelectricité, qui ne peut pas s’accumuler, constamment pen- 
dant un an de suite, dans un pais environné d’eau, ou tout 
concourt a mettre ce fluide en €quilibre. Il me reste le 
feu.” 
When we undertake to give a history of the eruptive state 
* of the bowels of the earth, we must commence that history 
with the actual existence of their inflamed state; for, al- 
though many volcanoes (which may be. termed pores or 
eruptive canals of the earth).are pot in an active state, and 
have been slumbering for hundreds of years, yet we have 
others that are seldom or never dormant—that of Stromboli 
been throwing out unremitted flames for two thousand 
“The earliest historians have given relations of many earth- 
quakes. Those of Pliny are among the best authenticated. 
In A. D. 79, Herculaneum was covered with lava seventy 
feet thick. Notwithstanding this continued ebullition, we 
find the surface of the earth but little changed by this agent, 
except in the immediate vicinity of volcanoes. 
e very strong reasons to believe that a conside- 
rable portion of the interior of ne earth is in a constant 
state of incandescence. In South America the bursting 
forth of one volcano is frequently followed by that of others, 
in the chain of the Andes at a great distance. So distinctly 
has this happened, that Humboldt considered this chain com- 
posed, not of different volcanoes, but of one immense vol- 
eanic wall stretching from north to south. The existence of 
this being before our eyes, it is easily to be supposed that 
larger and more extensive channels may exist at greater 
depths. Itis difficult, the same author says, “ not to admit 
the existence of cavities between the oxided parts of the 
globe—parts abounding in metalloids.”” ‘The extensive 
ranges that earthquakes frequently take go far to prove the 
existence of great channels of communication. Boyle, in the 
following quotation, expresses this opinion. 
“Tis the more likely that this earthquake shook great 
acts of land beyond those places to which the fired matter, 
, passing, from one cavity to tae tould Lremebe} in so short a 
time.” Royle, Vol. 1. p. 479. 
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