C 40 ] 



yet perhaps it might be inferior in another flate of the air, by- 

 magnifying the haze and vapors ; but the obfcrvalion of y Ser- 

 pentis in the glare of the fun on the 2d, and many ftars both by 

 night and day on the 4th, confirm the fuperiority of 600. 



I NEXT prepared a fet of diaphragms whofe areas of aperture 

 were inverfely proportional to the magnified area of the objed. 



December 12th, /3 Urfae minoris diftindl and magnified with 

 600 ; diftind alfo but not magnified with 200 : this flar is too 

 bright for any conclufion to be drawn. 



I ft y Urfse minoris, a very fmall ftar, vifible with 600, with its 

 proportional aperture J invifible with 400. v .'ji' 



Many other trials proved the fuperiority of the great magni- 

 fying power with diminifhed aperture : I cannot omit mentioning 

 one more. 



December 29th, /3 Lyras paffed 7' after the fun ; this ftar, of 

 the 3d magnitude, and fo near the fun, I had little expedation 

 of feeing. I fought it in vain with 200 and 400, but faw it 

 plainly and obferved its paflage wath 600, having an aperture 

 rather fmaller than juft proportion demanded. I fhewed the ftar 

 to another perfon before it quitted the field of view. 



For the fuperiority of magnifying power the following caufes 

 may be ailigned : 



The 



