50 Natural Histor)/ of Volcanos and Earlhquakes. 



of the Andes is said to be one of the latest, this cooling and 



contraction may continue even at the present time in that part 



which is within the earth. It is therefore possible to conceive 



that these eifectsare the cause of the frequent earthquakes in the 

 Ajides. 



Besides, there is nothing opposed to the hypothesis, that the 

 powers, whatever they may be, which produced so remarkable a 

 phenomenon as these elevations, may not even now operate in a 

 less degree, and occasion the earthquakes so frequent in the Andes. 

 The later these elevations are supposed to have taken place, the 

 more probable will such a hypothesis be. 



If further proofs are still necessary to show that the causes of 

 earthquakes are only to be sought in the interior of the earth, we 

 certainly find them in the fact, that these phenomena are totally 

 independent of external circumstances. They take place whether 

 the sky be clouded or serene, in hot as well as in cold weather,* 

 before or after rain, sometimes witli rain, and sometimes without 

 it. Even the strength and direction of the wind seem to have 

 no kind of connection with them.f Nor do they seem to be 



* Many observers allude, indeed, to variations of temperature of tlie atmos- 

 phere before and after earthquakes ; but the academicians of Turin only have actu- 

 ally made observations on the temperature in the county of Plgnerol. (Journ. de 

 Phys. t. Ixvii, p. 292.) They found that their thermometer always descended as 

 soon as shocks had been felt. Thus they felt a vehement shock in the morn- 

 ing at half past ten, on the 10th of April, and their thermometer descended till 

 noon from 26° to 22°. In fact it is to be desired, that farther observations should 

 be made on other occasions, in order to confirm or refute the assertion of so re- 

 markable a phenomenon. 



t The late F. Hoffman in vain endeavored to discover in the Meteorological 

 Journal of the Observatory of Palermo, (which included a series of years from 

 1792 to 1832, and where particular attention had been paid to the observation of 

 earthquakes, of which no less than fifty-seven had there been accurately observed,) 

 some peculiarity of weather, which might, with any degree of plau.sibiiity, bo 

 supposed to have been connected with the earthquakes. The same result was' ob- 

 tained by Doraenico Scina in his memoir on the numerous earthquakes, which, in 

 the years 1818 and 1819, caused so much appreliension in the neighborhood of the 

 Madonian hills —Poggendorrs Ann. t. x.xiv, p. 50 and 60. In contradiction to 

 this are the traditions current in many countries. See among others, Rrrghau's 

 Almanack, 1837, p. 97, and following. There seems to be in fact, some truth in 

 the opinion, that earthquakes are most frequent and vehement at the beginning of 

 rainy weather, and this phenomenon is even ascribed in Jamaica to a locking up of 

 the pores in the crust of the earth by water, which impedes the rising of gases. 

 On the other hand, cases have occurred in which eartli.piakes, were preceded by 

 a long continued droiight.-Barham in the Philos. Trans, t. xxx, p. 837 y 1718, 

 and t. xlix, p. 403 ; Relat. Hist. t. ii, pp. 273, 281, and t. v, p. 15, and 57 ; Hans 



