HEAT, COLD, AND LIGHT. 321 



namely, the producing of Light. For instance, 

 this is produced by the combination of resp. air 

 with phlogiston; and other instances might be 

 adduced. This strikes out an interesting subject of 

 philosophical inquiry. 



The fourth and fifth methods of producing 

 Ileat might be descanted upon very copiously j 

 but perhaps this would have but little tendency to- 

 wards determining what Heat is. 



Lastly, Heat is produced in volcanos. This has 

 commonly been supposed to be by burning of 

 fuel. But it is evident that it cannot be produced 

 by this cause, or by any other known means of the 

 production of Heat. The burning of fuel, it is 

 known, destroys a proportionate quantity of air : 

 to produce a very great degree of Heat requires 

 (till more to be applied than is naturally combined 

 with phlogiston. Now the whole island Santalina 

 is a mass of iron ore very difficult of fusion, 

 which was fused and thrown up from the bottorn, 

 of the sea in the midst betwixt two shore?, by this 

 Heat ; where no air could therefore possibly come. 

 And if it could, it would have required more in 

 quantity than would have exhausted the whole 

 atmosphere, to animate fuel enough to have pro- 

 duced the Heat. In Friesland, some time ago, 

 there was a tract of country 100 miles across, the 

 whole of which (wiih men, animals, trees, and 

 whatever was on it) was melted into one common 

 mass. This Heat then cannot be produced by 

 the burning of fuel ; much less can it be by the 

 decomposition of pyrites, which is indeed the 



burning 



