AA Natural History of Volcanos and Earthquakes. 
stances may be adduced. Firstly, as aqueous vapor is supposed 
to produce volcanic action, it must’ be presumed to be also the 
cause of earthquakes. Secondly, some hours before the first 
shock of the tremendous earthquake at Algiers and the neigh- 
borhood, the 2d to 5th March 1825, which entirely destroyed the’ 
town of Blisa, all the springs and wells are reported to have been 
dried up.* Thirdly, earthquakes, though undoubtedly felt even 
the centre of large continents, seem to produce their most fright- 
ful effects in countries not very far removed from the ocean. But 
perhaps, earthquakes may also be produced by gaseous exhala- 
tions in the interior of the globe. At least in many accounts of 
earthquakes, mention is made of the exhalation of gases from 
rents, produced by them,t+ and the smell of sulphuric acid, and 
of sulphurous vapors, which indicate the presence of sulphuret- 
ids. A cylinder 14 feet in height, and 31,395 pounds in weight, was to be cast. 
The clay mould having been totally filled up by melted iron, the latter broke 
through the ground, and penetrated to the depth of 25 feet into the sandy soil, con- 
sequently 11 feet deeper than the lower part of the mould. Some time after an 
equally violent shock happened, and after more than 24 hours a third followed. 
The local circumstances of that iron-foundery lead to an explanation of these 
phenomena. There are at a depth of 23-24 feet under the ground of the said 
building, many inclined channels which communicate together, for the purpose of 
collecting the rain water. Immediately after shocks, watery vapors issued 
abundantly from the mouth of the tk "These vapors were evolved by 
the heat of the melted iron from the water, being in the ground about two feet 
below the bottom of the channels; and penetrated through “the joinings of their 
brick work. But these joinings being filled up with mud and sand, offered re- 
sistance, and consequently the vapors had to attain a certain wong before they 
were able to penetrate through them. It is, however, very probable that the va- 
pors, bearing mud and sand with them, again stopped up the opening, when their 
slanivity sarelasty again decreased. During the shocks, the steam attained its 
greatest elasticity, and thickened the earth which surrounded the heated mass of 
iron; and this circumstance may have impeded a new afflux of water. Therefore, 
after the first shock, half an hour elapsed ; and after the second, which still more 
obstructed the afflux of the water, even more than 24 hours etapa before the 
third and latest shock took place 
* Berzelius, epg ht, 1827, p- 310 
t Von Humbol , Reise, t. i, p. 499. Vou Hoff in Poggend, Ann. t. vii, p. 292, 
¢. 2, p.593, t. xxv; i 76. V. Humboldt believes indeed, that daring : most earth- 
quakes, nothing arises from the earth ; but there are on the contrary, proofs that 
s are ofien gradually evolved from the ground before and after the shocks. 
The uneasiness of small animals, or those whose organs of respiration are rather 
feeble, before and after earthquakes, leads us to infer this. Le Gentil (Nouveau 
Voyage autour du Monde, t. i, p. 172) has already observed, that animals living ™ 
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