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Dr Sutherland, Liverpool. Communicated by the 

 Secretary. 



From a series of experiments made last summer, the author in- 

 fers, in confirmation of the results obtained by Young, Berard, and 

 Arago, that the chemical rays of light are subject to the same laws 

 of interference and polarization as its luminous rays. 



He found that the two images, produced by the sunbeam, and 

 also by its extreme violet rays, when refracted through a calc-spar 

 prism, quickly produce dark impressions, on being thrown upon photo- 

 genic paper, and that the extraordinary ray produces more effect than 

 the ordinary one. He then observed, by alternately extinguishing 

 and restoring the luminous rays with an analyzing apparatus of mica- 

 plates, that the plane of polarization of the chemical rays, as indi- 

 cated by the action on photogenic paper, corresponds with that of the 

 luminous rays. He next ascertained, that, by means of a section of 

 calc-spar rhomb, the polarized sunbeam, or the polarized violet ray, 

 could be made to produce, on photogenic paper, a series of pheno- 

 mena analogous to the coloured rings formed in the like circumstances 

 by the luminous rays. But the eifect of the violet rays was not so 

 perfect as might have been desired, owing to the want of a contriv- 

 ance for keeping the rays steadily for some time on the same part of 

 the paper during the change in the sun's position. 



The author farther found, that the chemical rays may be pola- 

 rized by reflexion, and then equally exhibit the general properties 

 which would be expected from a knowledge of those procured by the lu- 

 minous rays. The sunbeam, reflected from a mirror of glass-plates upon 

 an analyzing plate of flint-glass, and thence on photogenic paper, 

 was observed to have scarcely any effect ; but when the ray was ren- 

 dered capable of reflection, either by turning the analyzing plate on 

 its axis, or by interposing a plate of mica, a dark impression was 

 soon formed. 



Lastly, he ascei"tained that similar results might be procured by 

 means of repeated single refraction, which was accomplished by two 

 bundles of mica-plates so arranged in a tube as to admit of the planes 

 of the bundles being either placed at right angles to one another, or 

 made coincident. In the former case, the photogenic paper was not 

 affected, but in the latter, it was speedily darkened. By a similar 

 apparatus made of flint-glass, he succeeded in obtaining results of the 

 same kind with the light proceeding from the sky. 



