250 Researches in the Theory and Calculus of Operations. 



raences; and if the blows are repeated, the particles of the 

 hammered substance are condensed, and sensible heat is 

 evolved therefrom into the contiguous medium. An expla- 

 nation of the modus operandi of the calorific force in convert- 

 ing density into elasticity may be apprehended by attending 

 to the increasing oscillatory movement that would be pro- 

 duced in a freely suspended ball by the application of a uni- 

 form succession of light taps or slight mechanical impulses. 

 Each renewed impulse adds its effect to that of the preceding 

 one, and of course the amplitude of the oscillation of the 

 ball must increase. So the successive impulses of the Sun, 

 or of any heatecfr substance, impinging upon the substance 

 of an extraneous body, arouses reaction in the superficial 

 atoms of the latter, which is manifested by their rebound 

 from the compression inflicted on the interior atoms, and 

 consequent enlargement of the radius of elasticity. Thus 

 heat is a mode of motion (Tyndall). A strong application 

 of friction, much severer than that required for the produc- 

 tion of electrical effect, was early practised by the aboriginal 

 savages for the procurement of heat; a parallel instance of 

 the conversion of massive motion into molecular movement, 

 of rectilinear into vibratory movement, and distinguishable 

 from the method of educing electrical effects by reason of 

 the stronger compression which mechanically disturbs the 

 material particles. 



The comparative magnitudes of the calorific vibrations 

 peculiar to the three consistent states of ponderable matter 

 may be delineated thus : in the aerial state A (fig. 6), the 

 waves meet at their circumferences, and repulsion predo- 

 minates ; in the liquid state L, the circumferences meet at the 

 centres, and attraction and repulsion are balanced, the waves 

 being smaller and the body proportionally reduced in mag- 

 nitude; in the solid state S, the centres merge into their 

 own circumferences, attraction predominates, and the body 

 reduces to its minimum size. 



