SPEINGS OF KOCK-OIL, 143 



an immense volume of mud filled the crater, and 

 streamed down in a great torrent upon the val- 

 leys and plains beneath. In its course it filled 

 up the river courses, covered over hollows from 

 forty to fifty feet deep, and turned a fertile area 

 of land, forty miles square, into a desert. This 

 extraordinary eruption destroyed hundreds of 

 thousands of coffee-trees, many acres of rice- 

 fields, and, besides a vast number of inferior ani- 

 mals, overwhelmed not fewer than from ten to 

 eleven thousand human beings. In certain parts 

 of South America are volcanos which only emit 

 water and gas. They are called air-volcanos. 

 In all probability the " air " consists chiefly of 

 carbonic acid. The cut represents some of these. 

 We can give a somewhat more satisfactory 

 account of another natural phenomenon, in the 

 production of which the powers of the chemistry 

 of the interior are intimately concerned the 

 springs of rock-oil, or petroleum, or naphtha, 

 which are found in certain districts. It has 

 been found by experiment, that when pit-coal 

 is distilled with water, a certain quantity of an 

 oily liquid is obtained, which resembles in all 

 respects the mineral oil obtained from these 

 springs. Hence it is reasonably concluded, 

 that the production of this fluid is due when it 

 occurs in nature, to the action of heat upon beds 

 of coal under the surface, causing the petroleum 



