306 



5. " Researches tending to prove the Non- vascularity of certain 

 Animal Tissues, and to demonstrate the peculiar uniform mode of 

 their Organization and Nutrition." By Joseph Toynbee, Esq. Com- 

 municated by Sir Benjamin Brodie, Bart., F.R.S., &c. 



The above was only in part read. 



May 27, 1841. 



SIR JOHN BARROW, Bart., V.P., in the Chair. 



The Right Honourable the Earl of Carnarvon, and Ardaseer Cur- 

 setjee, Esq., were balloted for, and duly elected into the Society. 



The following papers were read, viz. — 



1. " On the Compensations of Polarized Light, with the descrip- 

 tion of a Polarimeter for Measuring Degrees of Polarization." By 

 Sir David Brewster, K.H., D.C.L., F.R.S., and V.P.R.S. Ed. 



In four papers published in the Philosophical Transactions for 

 1830, the author maintained, in opposition to the prevailing theory, 

 that light either reflected or refracted at angles different from that 

 at which it is completely polarized, does not consist of two portions, 

 one completely polarized, and the other completely unpolarized, 

 but that every portion of it has the same physical property, having 

 approximated in an equal degree to the state of complete polarization. 

 This conclusion, which had been derived from reasoning on the hy- 

 pothesis that a pencil of light, composed of two pencils polarized 

 respectively at angles of + and — 45° with the plane of reflexion, 

 was equivalent to a pencil of common light, is confirmed in this 

 paper by experiment, made with common light itself, reflected from 

 different parts of the atmosphere, and from which the uniaxal or 

 biaxal systems of rings were obtained. On placing such a system 

 between light partially polarized in an opposite plane, the author 

 found that the rings disappeared, the direct system being seen on one 

 side of the plane of disappearance, and the complementary system 

 on the other side. In this experiment the polarization of the light 

 in one plane was compensated by the polarization of the same light 

 in the opposite plane ; and, consequently, both the pencils, which 

 had undergone the two successive polarizing actions, had received 

 the same degree of polarization in opposite planes ; and in virtue of 

 these two equal and opposite polarizations, the light at the point of 

 compensation, where the system of rings disappeared, had been re- 

 stored from partially polarized to common light ; and the light on 

 each side of this point of compensation was in opposite states of 

 partial polarization. 



In order to give a distinct view of the nature of this experiment, 

 the author details the phenomena observed at particular angles of 

 incidence on glass. From the results at an angle of incidence of 

 24°, the ray suffering one refraction at 80°, and a second reflexion 



