528 Zoological Society. 



--id)- 



Consequently, by what has been just proved respecting N 

 and T, Jc will be different for right-handed and left-handed 

 circularly polarized light, but h will not be different, at least 

 will differ very little. In other words, the two kinds of light 

 will be propagated with different velocities, but will not be un- 

 equally absorbed ; which is a general explanation of the pecu- 

 liar effect of certain fluids upon circularly polarized light, and 

 by consequence, upon plane polarized light. 



N 

 We have assumed here that — is small compared with «, 



but it will do just as well to suppose that the absorbing power 

 of the medium is very small, in which case h may be regarded 

 as zero. All that is necessary is, that the two kinds of light 

 be not unequally absorbed by the substance, and yet be pro- 

 pagated with different velocities. 



We have thus shown that there is a certain hypothesis on 

 which the peculiar effects of certain fluids upon polarized light 

 may be generally accounted for. We do not however venture 

 to put this forward as the true hj'pothesis, as it is quite con- 

 ceivable that some other cause besides that we have supposed 

 might make N different for the two kinds of light, and h either 

 not different or extremely small. Since we must conceive the 

 particles of the fluid to be symmetrically posited in all direc- 

 tions, I think that the cause, whatever it be, must be some- 

 thing peculiar in the constitution of each individual particle, 

 which in some manner affeccs the resistance brought into ac- 

 tion upon the aethereal fluid. 

 Balham, Surrey, November 11, 1844. M. O'Brien. 



[To be continued.] 



LXXXV. Proceedings of hearned Societies. 



ZOOLOGICAL SOCIETY. 



Feb. 13, " A DDITIONAL Measurements of Blood-corpuscles or 

 1844 tA. Red Particles of Mammalia and Birds," by George 

 Gulliver, K sq., F.R.S., No. 2*. 



The measurements are expressed in vulgar fractions of an English 

 inch, according to the practice which I have always adopted. As 

 the numerator is invariably 1, it is omitted throughout, the denomi- 

 nators only being printed. 



* No. 1 will be found in the Proceedings of the Zoological Society, 

 No. cxix., Dec. 13, 1842, page 190. 



