ON ITS EXTEEIOK. THERMAL SPRINGS. 199 



coast chain, I saw the aguas calientes de las Trincheras 

 gush forth from a stratified granite which does not pass 

 into gneiss. I found the temperature of this spring, in 

 February 1800, 194-5,( 271 ) while the Banosde Mariara 

 in the Yalles de Aragua, which are in gneiss rock, showed 

 138*7. Three and twenty years later, again in the 

 month of February, Boussingault and Eivero ( 272 ) found 

 at the Mariara waters 147 0< 2, and at the Trincheras de 

 Portocabello, but little above the Caribbean Sea, in one 

 basin 198, and in the other 206'6. It would appear, 

 therefore, that in the short interval of little more than 

 twenty years, an unequal change of temperature had 

 occurred in these springs, the increase in the tempe- 

 rature of the Mariara waters being 8*5, and in that of 

 the Trincheras 12*1. Boussingault rightly called atten- 

 tion to the fact that the dreadful earthquake, which over- 

 threw the town of Caracas on the 26th of March, 1812, 

 took place in this very interval It is true that 

 at the surface of the earth the commotion was less 

 in the neighbourhood of the lake of Tacarigua (in 

 Nueva Valencia); but in the interior of the earth, 

 where elastic vapours act in clefts and fissures, may not 

 a movement propagating itself so widely, and with so 

 much violence, easily modify the network of fissures, 

 and open deeper channels for the access of heat ? The 

 hot waters of the Trincheras rising out of a granite for- 

 mation are almost pure, containing only traces of silica, 

 sulphuretted hydrogen and nitrogen. After forming 

 several very picturesque cascades, bordered by luxu- 

 riant vegetation, they become a river, the Eio de 

 Aguas calientes, which as it approaches the sea is full 

 of large crocodiles, the still high, though already 



