NATURAL HISTORY. 



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during the shocks at the borders 

 of the wells in the plain of Charas. 

 Water and sand are sometimes 

 thrown out twenty feet high. Si- 

 milar phaenomena have not escap- 

 ed the observation of the ancients, 

 w{»o inhabited parts of Greece and 

 Asia Minor abounding with ca- 

 verns, crevices, and subterraneous 

 rivers. Nature, in its uniform 

 progress, every where suggests the 

 same ideas of the causes of earth- 

 quakes, and the means by which 

 man, forgetting the measure of his 

 strength, pretends to diminish the 

 effect of the subterraneous explo- 

 sions. What a great Roman na- 

 turalist 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 subterraneous noise, so fre- 

 quent during earthquakes, is ge- 

 nerally not in the ratio of the 

 strength of the shocks. At Cu- 

 mana it constantly precedes them, 

 while at Quito, and for a short 

 time past at Caracas, and in the 

 West India Islands, a noise like 

 the discharge of a battery was 

 heard, a long time afler the shocks 

 had ceased. A third kind of phae- 

 nomenon, the most remarkable of 

 the whole, is the rolling of those 

 subterraneous thunders, which last 

 several months, without being ac- 

 companied by the least oscillating 

 motion of the ground. 



In every country subject to earth- 

 quakes, the point where, probably 

 by a disposition of the stony strata, 

 the effects are the most sensible, is 

 considered as the cause and the fo- 

 cus of the shocks. Thus at Cu- 

 mana the hill of the castle of St. 



Antonio, and particularly the emi- 

 nence on which the convent of St. 

 Francis is placed, are believed to 

 contain an enormous quantity of 

 sulphur, and other inflammable 

 matter. We forget, that the ra- 

 pidity with which the undulations 

 are propagated to great distances, 

 even across the basin of the ocean, 

 proves, that the centre of action is 

 very remote from the surface of the 

 Globe. From this same cause no 

 doubt earthquakes are not restrain- 

 ed to certain species of rocks, as 

 some naturalists pretend, but all are 

 fitted to propagate the movement. 

 In order to keep within the limits 

 of my own experience, I shall here 

 cite the granites of Lima and Aca- 

 pulco ; the gneiss of Caracas ; the 

 mica-slate of the peninsula of Ara- 

 ya ; the primitive thonschiefer of 

 Tepecuacuilco, in Mexico; the se- 

 condary limestones of the Appen- 

 nines, Spain and new Andalusia ; 

 and finally the trappean porphyries 

 of the provinces of Quito, and Po- 

 payan. In these different places 

 the ground is frequently agitated 

 by the most violent shocks ; but 

 sometimes in the same rock, the 

 superior strata form invincible ob- 

 stacles to the propagation of the 

 motion. Thus, in the mines of 

 Saxony, we have seen workmen 

 hasten up,afFright.ed by oscillations, 

 which were not felt at the surface 

 of the ground. 



If, in regions the most remote 

 from each other, primitive, secon- 

 dary, and volcanic rocks, share 

 equally in the convulsive move- 

 ments of the Globe; we cannot but 

 admire also, that in ground of little 

 extent, certain classes of rocks op- 

 pose themselves to the propagatiori . 

 of the shocks. At Cumana for in- 



