294 Dr. J. Hopkinson on the [June 14^ 



/3. A prism with two angles of about 45°, density =2*48664. 



The first line gives the mean observed indices, and the second the differ- 

 ences from the most probable values of a. 





A. 



B. 



C. 



D. 



E. 





Mean of observed values 



* ( 



1-572296 1-514156 

 0-000541) 0-000531 



1-515105 

 0-000537 



1-517623 

 0-000509 



1-520860 

 0-000529 



1-521474 

 0-000507 







F. 



(G.) 



a. 



h. 



H r 





Mean of observed values 



1-523657 

 0-000518 



1-528533 

 0000539 



1-528856 

 0-000503 



1-531439 

 0-000537 



1-533318 

 0-000526 



Soft Crown. — The prism has three angles from which the mean is taken, 



density =2-55035. 



«=0-5209904. 6 = 1-4034. c=-l-58. 





A. 



B. 



a 



D. 



E. 



b. 



Most probable value of p 





1-510916 

 1-510918 



1-511904 

 1-511900 



1-514591 

 1-514574 



1-518010 

 1-517991 



1-518686 

 1-518670 



Mean of observed values 



1-508956 



1-510918 



1-511910 



1-514580 



1-518017 



1-518678 







F. 



(G-.) G-. 



i 



h. H r 





Most probable value of fi 



1-520996 

 1-520994 



1-526207 1-526595 



1-526215 1-526603 



1 



1-529359 1-531416 

 1-529364 1-531418 



Mean of observed values 



1-520994 



1-526208 1-526592 



! 



1-529360 1-531415 



1 



Titano-silicic Crown. — This glass was made on the suggestion of 

 Professor Stokes in the hope of obtaining a glass of good quality which 



