NATURAL PHILOSOPHY. 153 



abundant as possible ; and in proceedino^ to throw tho water on 

 the nearest inflamed part, as soon as the lire ceases in that where 

 you began, till 3'ou have gone over all the burning parts as expe- 

 ditiously as possible. In thus regularly following the llames with 

 the water, they may be everywhere extinguished before the part 

 where you began has entirely lost, by evaporation, the water 

 with which it was wetted, which is frequently necessary, to pre- 

 vent the parts from taking fire again. After the flames of a burn- 

 ing body are extinguished, it cannot again take fire, for the above- 

 mentioned reason, till the water thrown upon it be evaporated. 



From what has been stated, it results, that to stop the most vio- 

 lent flame it is necessary only to wet the surface of the burning 

 substance where the flame appears, and for this purpose only a 

 small quantity of water is required, if it be applied with judgment 

 to the burning part. 



HEAT FROM BURNING GASES. 



The temperatures produced by the explosion of gases mixed in 

 definite proportions are not uniform. The highest degrees result 

 at first by the combustion of only a fraction of the mixture, and 

 the heat diffuses itself through the unaffected portion so as to 

 reduce the temperature to a much lower degree. Then, as the 

 mixture gradually cools oft\ another explosion takes place, resulting 

 in a temperature of a yet lower degree, and the last portion of the 

 mixture is only burnt when the temperature falls much lower still. 

 In the combustion of carbonic oxide in oxygen gas, both in proper 

 proportions, these three stages are at the temperatures of 5,491* F., 

 4,637'^ F. and 2,095* F. A mixture of equivalents of hydrogen 

 and oxygen, when exploded, rises to 5,151° F., and hydrogeu 

 with the corresponding quantity of atmospheric air, to 3,675^^ F. 

 Carbonic oxide, under the same circumstances, produces 5,500° F. 

 and 3,G25* F. Experiments with mixtures of carbonic oxide and 

 hydrogen gas with not quite sufficient oxygen showed the re- 

 markable fact, that these different stages of combustion result in 

 the formation of definite compounds, as in this case, of hydrates 

 of carbonic acid, in the following order : 2 CO2 + HO ; CO2 -j- HO ; 

 CO2-I-2HO; CO2 + 3HO; CO2 + 4HO; CO2 + 5 HO.— Bun- 

 sen, Foggendorff's Annalen, Vol. cxxhi. 



melting-point of fusible silicates. 



C. Sching finds, by a thermo-electric pyrometer, that silicates are 

 formed and melted at the same temperature, and that the forma- 

 tion depends more on time than on temperature ; that it dejDcnds, 

 in fact, on the conducting power of heat ]:)ossessed by the mate- 

 rials composing the silicates. He also finds the temperature re- 

 quired for melting metals and metallurgical products to be lower 

 than usually stated, 1,431*-1445°, for melting the same ; that the 

 temperature of a glass furnace in operation is only 1,100°-1,250° C. ; 



