194 



ductal*. Although we are not quite satisfied with this manner of 

 comparing the effects, because we consider that time enters very dif- 

 ferently as an element in the several cases, yet we are sensible of the 

 value of the experiments, and think that they strongly confirm the 

 author's conclusions as to the identity of electricities from different 

 sources. 



This series of experimental researches in electricity, we consider, 

 makes a very valuable addition to Mr. Faraday's former ones; and 

 we have no hesitation in recommending its publication in the Trans- 

 actions of the Royal Society. 



S. H. Christie. 



14th March 1833. 



May 9, 1833. 



WILLIAM GEORGE MATON, M.D., Vice-President, in the Chair. 



A paper was read, entitled, <c On the Anatomical and Optical Struc- 

 ture of the Crystalline Lenses of Animals, particularly that of the Cod." 

 By Sir David Brewster, K.H., LL.D., F.R.S. V.P.R.S.Ed. 



The author was led, by the observations he had made of some very 

 singular phenomena in the crystalline lenses of fishes and quadrupeds 

 when exposed to polarized light, to examine their minute anatomical 

 structure, with the view of ascertaining if it had any relation to these 

 optical appearances. He found that the crystalline lens of a cod has 

 the form of a prolate spheroid, of which the axis coincides with that 

 of vision. Its body is inclosed in an exceedingly thin and transparent 

 capsule, within which it flouts without having any apparent connexion 

 with that capsule, and consists of a hard nucleus surrounded by softer 

 matter. The nucleus is composed of regular transparent laminse of equal 

 thickness, with perfectly smooth surfaces, presenting the iridescent 

 appearance peculiar to grooved surfaces, and exhibited by mother- 

 of-pearl. These apparent grooves have the direction of meridian lines 

 converging from the equator, where their breadth is greatest, to the 

 two poles, and indicating the boundaries of the component fibres of 

 the laminae. The author was enabled to trace the course of these 

 fibres to their termination very satisfactorily, when the fibres them- 

 selves could not be rendered visible by the best microscopes, by means 

 of the reflected prismatic images of a luminous object, produced by 

 interference. This method furnished also an accurate mode of de- 

 termining the diameter of the fibres at any point of the spheroid. The 

 uniform distribution of the light refracted through the lamina, as well 

 as the distinctness of the reflected images, prove that these fibres are 

 not cylindrical, but perfectly flat, and gradually tapering in breadth 

 from the equator to the poles of the lens. The thickness of each fibre 

 is at least five times less than its breadth, which, in the most external 

 layer of the equator, is about the 5500th part of an inch. 



The observation of another optical phenomenon apparent on look- 

 ing at a bright light through a thin lamina of the lens of a cod, namely, 



