349 

 for that medium, and if it be permitted to represent dis- 

 persion by developing the velocity - of the transmission of 

 phase in a series of the form 



-=:Mo~Mi(y) 4.M2(y) -&c., (A)' 



then the velocity wherewith light of this colour conquers 

 darJcnesSi in this dispersive medium, by the spreading of 

 vibration into parts which were not vibrating before, is some- 

 what less than-, being represented by this other series 



Mo - 3mi (y )' 4- 5m2 (y y - &c. (B)' 



For other details of this inquiry it is necessary to refer 

 to the memoir itself, which will be published in the Trans- 

 actions of the Academy, and will be found to contain many 

 other investigations respecting vibrating systems, with ap- 

 plications to the theory of light. 



The two golden torques found at Tara, and exhibited 

 on a former occasion by Mr. Petrie (see Proceedings, 

 p. 274), having been purchased from Messrs. West by sub- 

 scription, they were this evening presented to the Academy 

 by Mr. Petrie, in the name of the subscribers. 



It was Resolved — That the Subscription List be printed* 

 in the Proceedings ; and that the marked thanks of the 

 Academy be given to those gentlemen, who, not being mem- 

 bers thereof, joined in the subscription. 



* It will be found under the head oi Donations. 



2h 



