292 British Association for the Advancement of Science. 



he had never found among his numerous examinations of the 

 lenses of fishes, any which are perfectly spherical, as they were 

 all either oblate or prolate spheroids, so that along the different 

 diameters of the solid lens, the vision would not be similarly per- 

 formed. But, independent of this circumstance, he stated that 

 in every solid lens there was only one line or axis in which vision 

 could be perfectly distinct, namely, the axis of the optical figure, 

 or series of positive and 7iegative luminous sectors, which are 

 seen by the analysis of polarized light. Along every other diam- 

 eter, the optical action of the lens is not symmetrical. When the 

 lens is not spherical but lenticular^ as in the human eye and in 

 the eyes of most quadrupeds. Dr. W. considers that the apparatus 

 for adjustment is the ciliary processes, to which this office had 

 been previously ascribed, though not on the same scientific 

 grounds as those by him discovered. One of the most impor- 

 tant results of Dr. W.'s dissections, is the discovery oi fibres in 

 the retina. These fibres may be rendered distinctly visible. 

 They diverge from the base of the optic nerve, and surround the 

 foramen ovale of Sommering at the extremity of the eye. Sir 

 J. Herschel had supposed such fibres to be requisite in the ex- 

 planation of the theory of vision, and it is therefore doubly in- 

 teresting to find that they have been actually discovered. Sir 

 D. concluded by expressing a hope that British anatomists would 

 turn their attention to this subject. 



Sir D. Brewster then communicated his researches on " J. New 

 Kind of Polarity in Homogeneous Light." At the last meeting, 

 said he, I gave an account of a new property of light, which did 

 not admit of any explanation. Since that time, I have had oc- 

 casion to repeat and vary the experiments ; and having found the 

 same property exhibited in a series of analogous though different 

 phenomena, I have no hesitation in considering this property of 

 light as indicating a 7iew species of polarity in the simple ele- 

 ments of light, whether polarized or unpolarized. After detail- 

 ing the experiments, he says, hence I conclude that the different 

 sides of the rays of homogeneous light have different properties 

 when they are separated by prismatic refraction or by the dif- 

 fraction of grooved surfaces or gratings ; — that is, these rays have 

 polarity. When light is rendered as homogeneous as possible by 

 absorption, or when it is emitted in the most homogeneous state 

 by certain colored flames, it exhibits none of the indications of 



