lIKIlt PHENOMENA. 
107 
Elastic fluids tlirown into the atmosphere may act locally 
on the barometer, not by their mass, which is very small, 
compared to the mass of the atmosphere, but because, at 
the moment of groat explosions, an ascending current is 
probably formed, which diminishes the pressure of the air. 
1 am inclined to think that in the majority of earthquakes 
nothing escapes from the agitated earth ; and that, when 
gaseous emanations and vapours are observed, they oftener 
accompany or follow, than precede the shocks. This cir- 
cumstance would seem to explain the mysterious influ- 
ence of earthquakes in equinoctial America, on the climate, 
and on the order of the dry and rainy seasons. If the earth 
generally act on the air only at the moment of the shocks, 
we can conceive why a sensible meteorological change so 
rarely precedes those great revolutions of nature. 
The hypothesis according to which, in the earthquakes of 
Cumana, elastic fluids tend to escape from the surface of the 
soil, seems confirmed by the great noise which is heard 
during the shocks at the borders of the wells in the plain of 
Charas. Water and sand are sometimes thrown out twenty 
feet high. Similar phenomena were observed in ancient 
times by the inhabitants of those parts of Greece and Asia 
Minor abounding with caverns, crevices, and subterraneous 
rivers. Nature, in her uniform progress, everywhere suggests 
the same ideas of the causes of earthquakes, and the means 
bv which man, forgetting the measure of his strength, pre- 
tends to diminish the effect of the subterraneous explosions. 
What a great Roman naturalist has said of the utility of 
wells and caverns* is repeated in the New World by the 
most ignorant Indians of Quito, when they show travellers 
the guaicos, or crevices of Pichincha. 
The subterranean noise, so frequent during earthquakes, 
* “ la puteis est remedium , quale et crebri specus prsebent : conceptum 
enim spiritum exhalnnt : quod in certis notatur oppidis, quae minus qua- 
tiuntur, crebris ad eluviem cuniculis cavata.” — Pliny, lib. ii, c. 82 (ed. 
Par. 1723, t. i., p. 112.) Even at present, in tlie capital of St. Domingo, 
wells are considered as diminishing the violence of the shocks. I may 
observe on this occasion, that the theory of earthquakes, given by Seneca, 
(Nat. Qusest., lib. vi., c. 4 — 31), contains the germ of everything that 
has been said in our times on the action of the elastic vapours confined 
in the interior of the globe. 
