On the structure of the crystalline lens in fishes and quadrupeds, as ascertained by its action on polarized light. By David Brewster, LL. D. F. R. S. Lond. and Edin. In a letter addressed to the Right Hon. Sir Joseph Banks, Bart. G. C. B. P. R. S

The author having found that in many instances depolarization depends upon variations of density in the bodies through which it is transmitted, concluded that corresponding effects would be produced by the crystalline lens of the eye, which is well known to increase in density towards the centre. By immersing the crystalline lens of a cod in Canada balsam, the refraction at its exterior surface was so far removed, that the effects of its internal texture could be examined independent of its external spherical form. Under these circumstances, when it was exposed to polarized light, with its axis of vision parallel to the beam of light, it exhibited three concentric circles of light separated by two dark circles, and intersected by a black cross so as to be divided into twelve luminous sectors. By varying the inclination of the axis, these appearances varied in a manner that can scarcely be described without the assistance of the drawings which accompany this paper.