TRANSIT OV MERCURY. Ijl 



(41.) Jan. 11, 1782. To all appearance, the morning 

 was very fine, but ftill the telefcope, when firft brought out, 

 would not ad well. After half an hour's expofure, it performed 

 better. 



Confined Place. 



(42.) July 19, 17S1. 13** 15'. My telefcope would not ad A confined pla«e 

 well; and, fuppofing the exhalations from the grafs in ^ytH^l^ilom' 

 garden to affe6l vifion, I carried the telefcope into the ftreet, afting wcjl, 

 (the obfervation was made at Bath,) and found it to perform 

 to admiration. 



(43.) July 19, 1781. My telefcope aded very well; but 

 a flight field-breeze fpringing up, and brufhing through the 

 fti^eet where my inftrument was placed, it would no longer 

 bear a magnifying power of 460. 



Hazinefs and Clouds. 



(44.) Sept. 22, 1783. The weather is now fo hazy, that Remarkable 

 the double ftar ^Cygni is but barely vifible to the naked eye.^^^^,"^!"^^^'"^ 

 This has taken ofl^'the rays of the large ftar, fo that I now fee 

 the fmall one extremely well, which at other times it is fo dif- 

 ficult to perceive, even with a magnifying power of 932. 



(45.) Auguft 13, 1781. A cloud coming on very gradually 

 upon fixed Itars, has this remarkable effed, that their apparent 

 diameters diminiili gradually to nothing, 



(46.) July 7, 1780. The air was very hazy, but extremely 

 calm. I had Ardurus in the field of view of the telefcope, 

 and, the hazinel's increafing, it had a very beautiful effeft on 

 the apparent diameter of this ftar. For, fuppofing the firft of One caufe of the 

 the points*, to reprefent the magnitude when bri^hteft, i apparent <iiame. 



r • ^^^ ^ r , ^ ., , . • o • - tCrS of the fixed 



law it gradually decreaie, and aliume, with equal diftm(5tnefs,ftars. 

 the form of ail the fucceeding points, from No. 1 to No. 10, 

 in the order of the numbers placed over them. The laft 

 niagni'ude I faw it under, could certainly not exceed two- 

 tenths of a fecond ; but was perhaps lefs than one. This leads 

 to the difcovery of one of the caufes of the apparent magnitude 

 of the fixt ftars, 



* Thefe pomts will be inferted in one of the plates in our next 

 number. N. 



Focal 



