Cambridge Philosophical Society. 429 
The Vice-President terminated his general and rapid sketch, in 
which he alluded to the brilliant discoveries of Brewster, Arago, and 
Fresnel, respecting the polarization of light,by observing that it would 
be needless for him to point out the important bearing of these facts 
on the question of the nature of heat, and its connexion with light. 
He concluded in the following terms :—“It now only remains for 
me to present to Professor Forbes the medal which has been award- 
ed to him for these discoveries. I believe that I shall be joined cor- 
dially by every member of the Society who now hears me, in the 
fervent wish that it may be the will of the Almighty Ruler, that his 
life may be long protracted, with vigour of mind and health of body 
to pursue the career in which he has made an advancement so ho- 
nourable to himself, and’reflecting lustre upon those great establish- 
ments, the University and the Royal Society, with which he is con- 
nected. I cannot doubt that he will persevere in this happy path 
with the same ardour and success which have hitherto accompanied 
his researches. Indeed, we have a gratifying proof that his zeal will 
not be impaired, nor his success less brilliant, from the discovery in 
the same field announced by him at the last meeting of the Society, 
of the Circular Polarization of Heat*.” 
CAMBRIDGE PHILOSOPHICAL SOCIETY. 
(Continued from p. 80.) 
Feb. 22.—A paper was read by Mr. Kelland, of Queen’s College, 
* On the application of the hypothesis of finite intervals to the expla- 
nation of the phenomena of dispersion.” The object of this paper was 
to show, that by supposing, as M. Cauchy has done, the distance 
between two consecutive particles of the medium of light to bear a 
finite ratio to the length of wave, the phenomena of dispersion are 
satisfactorily accounted for. Numerical calculations are entered 
into for the purpose of verifying the formula in all the cases which 
M. Frauenhofer has examined. The fact that a star appears to us as 
a point, and not a spectrum, compels the author to the conclusion 
that the medium of light is more dense in vacuo than in refract- 
ing media, a conclusion in opposition to generally received opinions, 
It is also a consequence of the above circumstance, as applied to 
the author’s formula, that the forces which the particles exert on 
each other follow the lawof the inverse square of the distance, and also 
that the vibrations must be transversal. The author added, that by 
the formula he had investigated, a marked difference was found in 
the results when applied to M. Frauenhofer’s seven solids and three 
* This discovery is announced in the Proceedings of the Society for Feb. 1, 
1836, in the following terms :—“ Professor Forbes verbally communicated 
to the Meeting, that he had succeeded in proving the Circular Polarization 
of Heat, whether accompanied or unaccompanied by Light, when polarized 
heat is made to undergo two total reflections within a rhomb of rock-salt ; 
the plane of total reflection being inclined 45° to the plane of primitive po- 
larization.” 
Prof. Forbes also announced his discovery in our Number for March last, 
at p. 248 of the present volume.—Eprr. 
