[ 42 ] 



that the efFed of the other angles on the image became infenfibic 

 to the eye. 



I SHALL conclude with pointing out an advantage that I reap 

 from this circumftance : By means of a confidcrable diminution of 

 aperture, 1 make the polar ftar fo diftindly round and large, that 

 I obferve the appulfe of its limbs to each edge of the wires, as 

 well as the pafTage of its centre over them ; by which means 

 much greater precifion is obtained in proving either the collimation 

 ■or meridian. 



I 



