PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 455 



that the formaha, representing the exact amount of force remaining, cannot 

 be given. 



Mr. Wiard read a paper in wliich he showed that the amount of force 

 required to condense a given vohime of gases, is the amount of heat force 

 employed in the dischai'ge of a gun. Part of this amount is expended in 

 heating the gun, part in vent and windage, while a large portion of heat 

 remained in gases as they escape from the gun at its discharge. 



Mr. Fisher directed attention to tlie effect of combined oxygen in a solid 

 state in combustibles. On comparing the amount of heat generated by 

 different kinds of coals, it is apparent that the presence of oxygen is not 

 advantageous, but that practically the amount of heat generated is in direct 

 proportion to the carbon and hydrogen in the coals; and as these combine 

 with oxygen of the air to produce heat, those portions previously combined 

 with ox3'gen, and existing in the solid state, must be regarded as having 

 ah'eady undergone the process of combustion. 



Mr. Rowell explained some experiments he was making to generate 

 steam by placing the stove or generator of heat under water, with a hot 

 blast to supply the fire with oxygen, and also to force the hot gaseous pro- 

 ducts of combustion through water, so as to save all the heat which is 

 commonly wasted through a chimney. 



The Cause of Heat. 



The Chairman remarked that we had often discussed the effects of heat 

 and the best manner of applying it in various branches of the arts, and it 

 would not be improper to turn our attention to the nature of heat. Up to 

 a late date heat had been regarded as an attenuated kind of matter, which 

 passed freely into and out of all ponderable bodies. This supposition was 

 strengthened by a corresponding view of light. The Dutch philosopher, 

 Huygens, boldly took ground against the opinions of Newton and his com- 

 peers, and asserted that light was the effect of the vibratory motion of au 

 extremely attenuated and subtle fluid which pervaded all space and per- 

 meated all matter. The manner in which this motion was performed was 

 still a mystery. There were certain phenomena which could not be ex- 

 plained by Huygens' theory; among these was that of double refraction. 

 By the splendid discoveries of Fresnal of France, who demonstrated that 

 the undulations producing light were transverse to the line of the ray, a 

 satisftictory explanation was given for all observed phenomena in relation 

 to light and color, and the undulatory theory was firmly established. The 

 discoveries of Fresnal regarding light awoke new interest as to the cause 

 of heat. 



The world is indebted to Benjamin Thompson, an American philosopher, 

 who spent neaidy all his life in Europe, and there received the title of Count 

 Rumford, for a satisfactory demonstration that heat is not matter. In 

 the year 1792, he published an account of his experiments in producing 

 heat by means of friction. His attention was first turned to this subject 

 on observing the vast amount of heat generated in boring cannon. He 

 accordingly constructed a cylinder, which was carefully surrounded with 

 non-conducting substances; in this was a closely fitting piston or plunge. 



