Second Letter from Dr. Hare to Prof. Faraday. 



1 



ball would be so refracted as to cross each other. Of the two 

 instances of illumination, thus imagined, would the one be de- 

 scribed as ordinary, the other as extraordinary radiation 1 But 

 if these epithets are not to be applied to radiation, wherefore un- 

 der analogous circumstances are they applicable to induction? 

 Wherefore is induction when acting through a plenum to be called 

 ordinary, and yet when acting through a vacuum to be called 

 extraordinary ? In the well known case of the refracting power 

 of Iceland spar, light undergoes an ordinary and extraordinary 

 refraction ; not an ordinary and extraordinary radiation. The 

 candle, of which, when viewed through the spar, two images are 

 seen, does not radiate ordinarily and extraordinarily. 



If there be occasionally, as you allege, (xxi,) large intervals 

 between the particles of radiant heat, how can the distances 

 between them resemble those existing between particles acting 

 at distances which are not sensible. The repulsive reaction be- 

 tween the particles of radiant caloric, as described by you, (xxi,) 

 resembles that which I have supposed to exist between those of 

 electricity ; but I cannot conceive of any description less suitable 

 for either, than that of particles which do not act at sensible dis- 

 tances. 



Aware that the materiality of heat, and the Newtonian the- 

 ory, which ascribes radiation to the projection of heat or light 

 producing particles, have been questioned, I should not have ap- 

 pealed to a doctrine which assumes both the materiality of heat, 

 and the truth of the Newtonian theory, had not you led the way ] 

 but, agreeably to the doctrine and theory alluded to, I cannot ac- 

 cord with you in perceiving any simihtude between the processes 

 of conduction and radiation. 



Consistently with the hypothesis that electricity is material, 

 you have shewn that an enormous quantity of it must exist in 

 metals. To me it seems equally evident that, agreeably to the 

 idea that heat is material, there must exist in metals a proportion- 

 ably great quantity of caloric. The intense heat produced when 

 wires are deflagrated by an electrical discharge, cannot otherwise 

 be consistently accounted for. Agreeably to the same idea, every 

 metallic particle in any metallic mass, must be surrounded by an 

 atmosphere of caloric ; since the changes of dimension conse- 

 quent to variations of temperature, can only be explained by cor- 

 responding variations in the quantity of caloric imbibed, and in 



