181 



of all degrees of refrangibility, that is for all values of y, is least in 

 the plane of greatest polarization and greatest in the plane at right 

 angles — contrary to the idea of Moigno, who, for insufficient rea- 

 sons, imagined that the maximum occurred in the plane of polariza- 

 tion and the minimum in the plane at right angles. 



The yellow tint in the position of minimum intensity, and the vio- 

 let tint in the position of maximum intensity, is nevertheless per- 

 fectly accounted for by the consideration that y is greater for the 

 violet and indigo rays than for the red and yellow. 



The paper further contains some observations respecting a subjec- 

 tive centre of the eye, distinct from the usual objective centre, which 

 may be read with interest, as they remove some difficulties con- 

 nected with the theory of vision, which had often occurred to the 

 author, and may have occurred to others. 



March 9, 1857. 



Mr. Hopkins gave an account of some experiments on the conduc- 

 tivity of various substances, and pointed out the bearing of the results 

 on theories of terrestrial heat. 



April 27, 1857. 



Mr. Humphry read a paper " On the Proportions of the Human 

 Frame." 



May 11, 1857. 



A paper was read by Professor Stokes, " On the Discontinuity of 

 Arbitrary Constants which appear in Divergent Developments." 



In a paper " On the Numerical Calculation of a class of Definite 

 Integrals and Infinite Series " printed in the ninth volume of the 

 'Cambridge Philosophical Transactions,' the author succeeded in put- 



T 00 7T 



ting the integral I cos - (w 3 — mw)dw under a form which admits of 



Jo 2 



receiving every numerical calculation when m is large, whether po- 

 sitive or negative. The integral is obtained in the first instance under 

 the form of circular functions for m positive, or an exponential for 

 m negative, multiplied by series according to descending powers of 

 m. These series, which are at first convergent, though ultimately 

 divergent, have arbitrary constants as coefficients, the determination 

 of which is all that remains to complete the process. From the 

 nature of the series, which are applicable only when m is large, or 

 when it is an imaginary quantity with a large modulus, the passage 

 from a large positive to a large negative value of in cannot be made 



