COMBUSTION AND DEFLAGRATION. 13' 



ponderable matter, result from their mutual affi- 

 nity : while the escape of caloric during com- 

 bustion, or deflagration, results from the dimi- 

 nution of that affinity, for the same reason that 

 the volume and elastic force of hydrogen and 

 nitrogen greatly augment on the decomposition 

 of ammonia. 



There is nothing more"clearly demonstrable in 

 science, than that all the caloric evolved during 

 the decomposition of ponderable matter, whether 

 solid, liquid, or gaseous, is only a liberation of 

 what was previously concentrated around the 

 atoms of the materials employed. When the 

 particles of solids are separated and subdivided 

 by friction, or collision, a portion of their con- 

 centrated caloric is disengaged, producing incan- 

 descent sparks, or streams of fire. 



A machine is exhibited at the Hall of Practical 

 Science in London, which illustrates the enor- 

 mous quantity of caloric in steel, and its evolution 

 by decomposition, in the most beautiful and strik- 

 ing manner. A circular plate of soft iron is made 

 to revolve at the rate of 5000 times per minute, 

 when the hardest steel on being applied to its 

 edge is cut through rapidly, and reduced to in- 

 conceivably small particles, which are still farther 

 expanded by the caloric thus liberated, into a 

 shower of metallic flame and sparks. This kind 

 of ignition proceeds equally well in vacuo, as in 

 the atmosphere. 



