112 EXPANSION AND CONTRACTION 



volumes of ammonia, the elastic force of which 

 is so far diminished that it may be condensed 

 into the liquid state by a pressure equal to 6'5 

 atmospheres, or by cold alone at the tempera- 

 ture of 46 below F. And when 2 volumes of 

 nitrogen combine with 1 of oxygen, the elastic 

 force of the resulting compound gas is so far dimi- 

 nished, that it may be liquified by a pressure 

 equal to 44 atmospheres at the temperature of 

 32, as first shewn by the experiments of Sir H. 

 Davy ; or by a pressure equal to 50 atmospheres 

 at the temperature of 45, according to Faraday. 

 What then is the rationale of these curious phe- 

 nomena ? Is the sphere of repulsion in the ele- 

 mentary gases exchanged for one of attraction 

 as they unite chemically, with contraction of 

 volume and diminution of elasticity? Or how 

 many immaterial and imaginary spheres of at- 

 traction and repulsion are required to explain 

 the phenomena of solidity, liquidity, and gase- 

 faction ? The summary answer to these queries 

 is, that " the self repulsive power of caloric is 



the same law of expansion is true of atmospheric air and hydrogen , 

 up to the temperature of 680 ; from which they concluded, that 

 it was true of all gases, and at all temperatures. (Ann. de Chim. 

 et Phys. vii. 120.) Dr. Dalton also found that the elastic force 

 of steam was equal to the weight of the atmosphere at 212, but 

 was equal to the pressure of 135 atmospheres when raised to 320. 

 And we learn from the experiments of Perkins, that when water 

 is confined in very strong vessels it expands with a force equal to 

 the pressure of 1050 atmospheres when raised to the temperature 

 of 419. 



