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An Account of fome OBSERVATIONS made with a view 

 to a/certain whether MAGNIFYING POWER or 

 APERTURE contributes moji to the dijcerning fmall Stars 

 in the Day. By the Rev. HENRY USSHER, D. D. 

 M.R.I.A. and F. R. S. 



XT has long been a difputed point amongft aflronomers, nor is it, Read Feb. 

 I believe, yet decided, whether aperture or magnifying power 2,1788. 

 contributes moft to the difcerning fmall ftars in the day. 



The following experiments and obfervations, made with the 

 tranfit inftrument of our obfervatory, may perhaps tend to-throW 

 fome hght on the fubjed : they were made with care, and are 

 certainly related without prejudice, for the conclufion I arrive 

 at, is contrary to what I fuppofed previous to experiment. 



The tranfit inftrument of the obfervatory is furnifhed with 

 three different lyftems of eye-glaffes, making the magnifying 

 powers of the inftrument about 200, 400 and 600. Thefe 

 fyftems being conftruded by Mr. Ramfden upon the principle 



indicated 



