442 MECHANICAL AGENCIES OF 



spark from a Leyden battery may be passed 

 through gunpowder without igniting it, unless 

 retarded in its progress by an imperfect con- 

 ductor, such as water, when it inflames gun- 

 powder. When electricity of high tension passes 

 without interruption through conductors, it does 

 not heat them ; whereas, if they be too small to 

 allow its free passage, or if the conductors be 

 imperfect, they are heated, fused, and volati- 

 lized. The same is true of solar caloric, when 

 concentrated by a large burning glass, which 

 passes through water and other transparent sub- 

 stances without heating them ; but if made to act 

 on bodies that obstruct its passage through them, 

 they are fused, ignited, and dispersed in the form 

 of flame. 



It has been a leading object of this inquiry 

 to show how partial and erroneous is the pre- 

 vailing notion, that the agency of caloric is limited 

 to the production of temperature, liquefaction, 

 combustion, &c. It is to its power of producing 

 motion, and of maintaining the harmonious action 

 of all the elements, that we are to seek for the 

 laws which connect it with the science of uni- 

 versal nature. 



I have pointed out its mechanical agency in 

 steam, by which it produces every variety of 

 motion, horizontal, vertical, and rotatory and 

 by which it has given to man a power over matter 

 superior to all the achievements of ancient or 



