94 REPORT—1863. 
results; nor has it been but tried to subject the whole field to a systematic 
survey, by which future investigators might be guided in their researches, 
1, The discovery of Prof, Stokes is well known to haye consisted in this :— 
He found that very many substances, upon the incidence of invisible rays of 
greater refrangibility than the violet, scattered visible rays, and were thence 
rendered perceptible to the eye, in what would otherwise have been complete 
darkness; and also, that most of such substances, upon the incidence of ordinary 
visible rays, had the power to produce, in the diffused (or re-emitted) beam, 
other visible rays, of less refrangibility than the incident, Such substances 
Prof. Stokes called fluorescent, Now the above facts naturally suggest several 
questions, to explain which briefly and clearly it is necessary to advert to 
the constitution of the solar or other similar spectra as evolved by a neu- 
tral or non-absorbent prism. Every such spectrum consists of three com- 
partments, distinguished by physiological—or generally, extrinsic—rather 
than intrinsic peculiarities, but which it is yet necessary for present purposes 
to consider separately. In order to avoid the mischievous ambiguity attendant 
on the adoption of the terms actually in use, it is proposed to employ in the 
sequel the following new nomenclature as applied to the three compartments 
of the spectrum, and the species of rays which each of them contains. The 
medium compartment, and the visible rays of which it consists, will be called 
Newtonic; the compartment bordering on the red end of the Newtonic, and 
the invisible rays composing it, will be called Herschellic ; finally, the com- 
partment bordering on the violet end of the Newtonic, and the similarly in- 
visible rays of which it is composed, will be called Aitteic—the name given 
being formed in each case from that of the first discoverer of the given species 
of rays, 
2. Considering the different nature of rays as just described, and the con- 
vertibility of some of them into others of a different refrangibility exhibited 
in the phenomena of fluorescence, the question, implying seyeral distinct pro- 
_ positions, must naturally arise in the mind whether, upon the whole, changes 
in regard to wave-length and refrangibility, or transmutations of rays corre- 
sponding in number and kind to the following list, may not either spon- 
taneously occur in nature, or be capable of production by experiments specially 
directed to the purpose, yiz, :— 
Transmutations 
1. of Ritteric rays into less refrangible Ritteric rays, 
2. a ne | Newtonic rays, 
3 foi) Herschellic rays, 
3. } 
4. of Newtonic ” 9 Newtonic rays, 
” 5) Herschellic rays, 
6. of Herschellic 5 Herschellic rays ; 
9) 
also 7. 5 » more refrangible Herschellic rays, 
8. » ” (G;) Newtonic rays, 
9. ” » (,:) Ritteric rays, 
10. of Newtonic A Newtonic rays, 
: ” 33 (;) Ritteric rays, and 
12. of Ritteric 2 3, Ritterie rays. 
8. Of the enumerated list, the transmutations (2) and (4) belong to fluo- 
rescence; the question of feasibility extends, hence, only to the remaining 
ten. Of these, the transmutation(8) deserves most attention, as being, at once, 
the counterpart of (2), and implying, equally with the latter, a conversion of 
invisible rays into visible. But, since both the species of transmutations ac- 
