OF AETS AND SCIENCES. 



387 



Since R^' -f 2.8;^ = A, we have 



G^b^ —3.8/4 = ^ 



G^H^-\-AAyi = A 



COMPARISON OF YARDS R^X G^\ 6V'«, AND G^^^, WITH ONE- 

 INCH OBJECTIVE- 



Since ^i"=— 1.4^ = 



