0^4 FHILOSOPHICAL TRANSACTIONS. [anNO 176^. 



The concave and convex tools should be ground with fine emery, after you 

 have done one side of the glass, for the oftener these are ground together, you 

 will be the more sure of having the figure true. 



EKD OF THE FIFTY-NINTH VOLUME OF THE ORIGINAJL. 



END OF VOLUME TWELFTH. 



C» and R< Baldwin. Prtotere, 

 New Bridgt-Strett, Lortion. 



