32 Dr. C. K. Akin on Calcescence. 



substance, a certain heating power, which depends (1) on the 

 amplitude of the given ray, (2) on the absorptive power of the 

 given substance for the given ray, and (3) in some unknown 

 manner on the length of undulation of the given radiation. Any 

 kind of radiation may hence be competent to raise any substance 

 whatever to any required temperature by a suitable adjustment 

 of the element of amplitude alone, provided the substance consi- 

 dered be not absolutely pervious to, or an absolute reflector of, 

 the given radiation ; more particularly must any species of New- 

 tonic or Ritteric radiation be competent to raise any metal to 

 the fixed temperature of incandescence, if the radiation have 

 sufficient amplitude and be not of that quality which exception- 

 ally may render it liable to absolute reflexion. The conclusions 

 here stated are warranted by all our present knowledge regard- 

 ing the nature of heat, temperature, and radiations. For, how- 

 ever small may appear the calorific effect of the more refran- 

 gible part of an ordinary solar spectrum — whether this be owing 

 to the comparatively small amplitude of the radiations compo- 

 sing it (which we are unacquainted with), or to the peculiar 

 nature of the undulations, which renders them less absorbable or 

 otherwise unfit to produce as great heating effects as the less re- 

 frangible radiations, independently of the effects of dispersion — in 

 no case where actual absorption takes place can this heating effect 

 be absolutely nought *. But metals, by the teaching of experience, 

 do absorb both Newtonic and also Ritteric raysf, the heating 

 effect of which, by an increase or addition of amplitude, may 

 hence be augmented to any wished-for degree, and more parti- 

 cularly be made to result in incandescence — theoretically, and 

 saving practical difficulties. 



The above considerations clearly demonstrate that, if no other 

 reasons militated to the contrary than the apparent results arrived 

 at by experimenters, it were right to class the metals among 

 fluorescent and also among phosphorescent substances ; and, in 

 the next place, what is even more important, that, by means of 

 metals at any rate — and probably by the very substances hitherto 

 distinguished as fluorescent — the opposite transmutations of 

 those which are ordinarily effected by fluorescent matter, and 

 which were believed to be alone possible, might be realized. 

 For it will be evident that incandescence, or an emission of New- 

 tonic rays, which, as proved, might be engendered even by Rit- 



* Compare the interesting experiments and remarks by Dr. Draper, in 

 Phil. Mag. vol. i. pp. 93-95 (1851). [It is supposed of course that the ab- 

 sorption does not produce any chemical or other similar effects.] 



f With regard to Newtonic rays, the colour of metals is a sufficient proof 

 of their absorptive power. For proof of the absorptive power of metals with 

 regard to Ritteric rays, see the observations by Prof. W. A. Miller, in Proc. 

 Roy. Soc. No. 51. p. 163 (1862). 



