and in the Condensation of Vapours. 409 



It is also very probable that it is at a temperature 

 which is invariable that the oxygen and hydrogen are 

 disposed to approximate and unite in order to form an 

 atom of vapour, and that the intensity of the heat devel- 

 oped at the moment of this union is also invariable, and 

 that it is always manifested in all its intensity in the 

 atom of vapour which is formed. 



But as the atom of vapour is extremely small, and sur- 

 rounded by bodies relatively very cold, its heat is soon 

 dissipated. 



There is, however, a method, which appears certain, 

 that we may employ in order to determine the tempera- 

 ture of an atom of vapour at the moment of its forma- 

 tion, and by this means we may know what is the high- 

 est temperature which it is possible to procure by means 

 of combustion. 



We have seen that, according to the results of the 

 researches of Dr. Crawford, it seems that when i 

 pound of hydrogen is burned, enough of heat is de- 

 veloped on this occasion to elevate the temperature 

 of 410 pounds of water 180 F. (= 100 degrees cen- 

 tigrade). 



Now as i pound of hydrogen perfectly dry is united 

 by burning to 7.3333 pounds of oxygen, and forms 

 with it 8.3333 pounds of steam, it is evident that 

 the quantity of heat which' exists in 8.3333 pounds of 

 steam at the instant when this steam is formed, is 

 equal to that which is necessary to raise the temperature 

 of 410 pounds of water 180 F., or to elevate the tem- 

 perature of 73,800 pounds of water one degree of the 

 scale of Fahrenheit. 



From this calculation we may conclude that the quan- 

 tity of heat which exists in i pound of steam, at the 



