MITCHILL ON THE EARTHQUAKES AT VENEZUELA. 309 



sixty toises (three thousand three hundred and sixty feet) high. This 

 elevation renders the region one of the most excellent and agreeable 

 upon the globe, although its latitude is no more than eleven degrees 

 thirty minutes north. 



The base of Mount Sylla is calcareous, approaching, in many places, 

 to the character of lime or chalk; and of a micaceous substance inter- 

 mixed with primitive rocks, and interspersed with metallic veins contain- 

 ing bismuth, plumbago, antimony, iron, and even small quantities of 

 copper and silver. Plants and shrubs scarcely grow upon it; and the 

 bare and parched sides of this and the other mountains which form the 

 borders of the valley of Caraccas, make a most striking contrast with 

 the fertility and luxuriance below. And what is very remarkable, in 

 this mountainous region the earth abounds with saltpetre ; insomuch that 

 Mr. Ponsard, after having satisfied himself of the fact, was occupied in 

 establishing a manufacture of the article, when the earthquake laid his 

 works in ruins. 



These subterranean commotions are supposed not to have been the 

 first which Venezuela has experienced. From the testimonials extant, 

 there is reason enough to conclude, that the country has undergone 

 violent convulsions in times more remote than the date of history. 



During passion week, on holy Thursday, at 4 o'clock in the afternoon 

 of the 26th day of March, 1812, while the streets of Caraccas were 

 filled with processions, and the churches with priests and people, and 

 while the ceremonies of flagellation and bearing the cross were per- 

 forming, a most destructive earthquake occurred. The cracking of 

 houses, and the descent of tiles, as if acted upon by a gust of wind, were 

 the first notices of it. As the atmosphere was calm, and not a breath 

 of air was stirring, the cause was instantly conjectured. 



The shocks succeeded each other with incredible rapidity; and 



