102 ; REPORT— 1863. 
ating bodies, by the agency of certain kinds of matter, has been principally 
brought into notice through Prof. Stokes’s discovery of fluorescence. Itis true 
that already Benjamin Wilson contended, against Beccaria*, that the light of 
phosphorescent substances is generally independent as to colour, of the colour 
of the incident light. It is true also that Wilson sagaciously remarked that 
the emission of the light of phosphorescence must take place during as well 
as after action on the part of the active incident light, though it may ordi- 
narily be hidden from observation by the greater intensity of the non-reno- 
vated, non-transmuted, diffused light+; both which facts, that referring to 
colour as well as that referring to time, were clearly proved by the later ex- 
periments of Grosser on diamondst. It is true, finally, that Seebeck had 
noticed phosphorescence produced by rays near the violet border of the spec- 
trum, of doubtful visibility, and hence pertaining, perhaps, to the Ritteric 
compartment§; that M. Matteucci and M. E. Becquerel, later, actually ob- 
served phosphorescence to occur in regions of the spectrum undoubtedly 
forming part of the Ritteric compartment||; as also, lastly, that M. E. Bec- 
querel, in one or two instances, noticed the occurrence of such phosphorescence 
during the time;’of incidence of the active Ritteric rays. Still, phospho- 
rescence, before the time whence Prof. Stokes’s experiments date, was princi- 
pally considered as a phenomenon interesting in so far as showing an emission 
of light, without reference to colowr, consequent upon and after exposure of the 
given substance to incident light. It was Prof. Stokes’s discovery, arrived at 
from quite a different and apparently unpromising starting-point, which first 
drew general attention to the change of refrangibility which Newtonic as well 
as Ritteric rays may undergo whilst incident on properly selected matter**. 
This, in the end, taught us to consider phosphorescence as only a species of the 
phenomena just described, distinguished for the protraction of the state of 
emission by renovation beyond the duration of incidencet?. But this quality, 
to which at first had attached the principal interest, now may be considered 
as of secondary importance. 
The most general law relating to fluorescence, including phosphorescence, 
has been already adverted to in the preceding part, and is generally expressed 
* (Beccaria) Phil. Trans, 1771, p. 212. (Wilson) Journ. de Phys. vol. xv. p, 93 (1780). 
The same fact which Wilson maintains, had been experimentally established in 1728 by 
Ae acting upon the suggestion of F. Zanotti (see Comment. Bonon. vol. i. p. 203). 
(Wilson) 7. c. p. 95. The original work of Wilson on phosphorescence, of which two 
editions seem to have been published, the author has not been able to consult. 
t Journ. de Phys. vol. xx. p. 277 (1782). 
§ Ibid. Comptes Rendus, vol. xiv. p. 903; being the translation, by Arago, of a passage 
from the Appendix to the original edition of Goethe’s ‘ Farbenlehre.’ 
|| (Matteucci) Bibl. Univ. vol. xl. p. 161 (1842). (H. Becquerel) ibid. p. 360; also Tay- 
lor’s Scientific Memoirs, vol. iii. p. 552 (1843). 
Ann. de Chim. et de Phys. vol. ix. p. 320 (1843). 
** The fact, likewise, that liquids, like solids, may act as ray-renovators, was first of all 
established through the discovery of Prof. Stokes. 
+t Cf. Engl. Cycl. (Arts and Sciences) vol. iv. p. 124. Now that the identity, in the main, 
between phosphorescence and fluorescence has been pointed out, some further facts may be 
adduced in support of the theory of fluorescence advanced in Part{I. Art. 6. Of these new 
facts, the most interesting (which was first observed by Benjamin Wilson, and later again 
by Seebeck and others) is the negative or extinguishing action of little-refrangible Newtonic 
rays upon the state of luminosity of phosphorescent bodies. Another observation, by Can- 
ton (see Phil. Trans. 1768, p. 341), has shown the influence which temperature, and hence 
the spontaneous rays of bodies, have on the duration of phosphorescence ; which influence, 
according to M. E. Becquerel (see Ann. de Chim. et de Phys. vol. ly. p. 102, 1859), extends 
also to the colour of the light emitted. All these facts tend to prove that the rays emitted 
by renovation are owing to a kind of interference between the incident and spontaneous ; 
but it would not be difficult to test this view by some more direct experiments. . 
