358 



I have mentioned, entirely disappears, and it is then easy to con- 

 vince one's self that the ends B and b are not only extremely indistinct, 

 but completely separated when the optic axes are converged upon A 

 and a united and seen distinctly. 



*' You will oblige me by reading these few and hurried observa- 

 tions to the Society. I differ with Mr Rogers on many other points 

 to which I shall have occasion to refer in a treatise on the Stereo- 

 scope which will soon be published. I am, &c. 



" D. Brewster. 



I " St Leonard's College, St Andrews, 

 February 16, 1856." 



2. Theory of the Free Vibration of a Linear Series of Elastic 

 Bodies. Part I. By Edward Sang, Esq. 



Some remarkable Specimens of Photography were exhibited. 



The following Gentleman was elected an Ordinary Fel- 

 low : — 



Dr Laycock, Professor of the Practice of Medicine. 



The following Gentleman was elected an Honorary Fel- 

 low : — 



Henry D. Rogers, Esq., State Geologist of Pennsylvania, U.S. 



Monday i Zd March 1856. 



Dr CHRISTISON, Vice-President, in the Chair. 



The following Communications were read : — 



1. Observations on the Diatomaceous Sand of Glenshira. 

 Part II. Containing an Account of a number of ad- 

 ditional undescribed Species. By William Gregory, 

 M.D., F.R.S.E., Professor of Chemistry in the Univer- 

 sity of Edinburgh. 



The author, after referring to his former paper on this subject, 

 stated that he had continued the investigation, and that the number 

 of undescribed forms besides those formerly figured had proved so 

 large, that the present paper does not conclude the subject, but that 



