44 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,f 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 

 earthquake actually took place, which shook the whole building so violently, that 

 the workmen feared it would be seriously injured. About half an hour 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 the shocks, watery vapors issued 

 abundantly from the mouth of the channels. 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 elasticity before they 

 were able to penetrate through tiiem. It is, however, very probable that the va- 

 pors, bearing mud and sand with them, again stopped up the opening, when their 

 elasticity gradually 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 afllux 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 elapsed before the 

 third and latest shock took place. 



* Berzelius, Jahresbericht, 1827, p. 310. 



t Von Humboldt, Reise, t. i, p. 499. Von Hoff in Poggend. Ann. t. vii,p. 292, 

 t. ix, p. 593, t. XXV, p. 76. V. Humboldt believes indeed, that during most earth- 

 quakes, nothing arises from the earth ; but there are on the contrary, proofs that 

 gases are often 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 (INouveau 

 Voyage autour du Monde, t. i, p. 172) has already observed, that animals living in 



