^. 



28 



MATHEMATICAL and 



'<' The idea I had formed of the contact was — That Ve- 

 nus would inftantancofly make a well defined black and 

 ftnall impreffion or dent on the Sun. But this" appearance 

 was fo different, the difturbance on the limb fo ill defined, 

 undulatory, pointed, waterifh, and occupying a larger 

 fpace than I expedcd, that I was held in a fufpcnfe of 5'' 

 or 6'^ to examine whether it might not be fome fkirt of a 



watery flying cloud. 



" Perceiving this Ihadow (atmofphere, or whatever clfe 

 it was) to prefs ftill forward on the limb, with the fame 

 tremulous pointed appearance, the longeft points towards 

 the middle, I began to count the beats of the clock for 

 either 15" or 16% when a well-defined black dent, appa- 

 rently occupying a lefs fpace on the Sun's limb, became 

 diftindly vifible. I then quitted the, telefcope and turning 

 to the clock, noted the time it then ftiewed, which was 2\ 



? 



V 



^ 



f 



11 



12' 5 



" About 22" fooner than this (viz. the 16'' I counted, 

 and the s" or 6^' in which I remained in doubt at the be- 

 ginning) vs^as the firft vifible impreffion on the limb which 



my telefcope would flicw; and I alfo marked that time 



down : viz. 2^ 1 1' ^o" to 43^ If this firft impreffion is 

 to be taken for the external contaSi-^ I think it may be 

 judged of almofi: to ?iftngle fecond, by perfons having 



equally good eyes and telefcopes; which cannot be done, 



as I apprehend, to federal fecotids-, either with refped to 

 the internal contaB^ or even with refped to the moment 

 of the firft diftind black dent, commonly marked for the 

 external contatl. In both thcfc, fome differences may 

 well happen among the bcft obfervers, from their different 

 manner of judging, in refped to a circumftancc of fuch 



exquifite nicety. 



Whether a telefcope of larger powers than what I 

 made ufe of, might not have fooner fliewn this firft ftia- 

 dowy Impreffion (that preceded the diftind black contad) 

 I will not take upon me to determine; though, from the 



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Mr. Rittcnhouft 



But this 

 I can 



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