"- x-^^ 



■I r-^. j-r ■ ■ -jr-^ 



/ 



aS 



M A 1"^ li E M A T I C A L and 



s 



at 2\ 28/ 45^ by the clock (when the appearance of rif?^^' 

 and the border of light where as la fig. 3. plate 3.) and 

 immediately began to count feconds, which anyone who ha 

 been accuftomed to it, may do for a minute or two, pretty- 

 near the truth. In thiii manner I counted no lefs than 1 

 32'''' before the cffc£l ofthc atmofphcre of r^m^j- on the 



n's limb wholly difappearcd ; leaving that part of the 



11 defined as the reft. From this I concluded 



O Li 



limb as we , 



that I had given the fignal for the internal contaB too foon; 



and the times given by the other obfervers at Norriton 



confirm me in this opinion." 



Mr, LUKENS'j Account of the Contads. 

 *' The telefcope 1 ufed, being a refrador of 42 feet,, 

 giving but a fmall field, and fomething difficult to manage, 

 by reafonofthe Sun's great altitude; I was obliged to 

 move t often, and apprehend that I did not difcover the 

 firft impreifion of the planet on the Sun, which my tele- 

 fcope would havefliewn. For, after one of thofe movements, 

 on bringing the glafs to bear again on that part of the Sun's 

 limb where Venus was expe£ted, I faw a large tremulous 

 ihadow, already fome what advanced, and feeming to prels 

 ftill inwards on the Sun's limb. Having contemplated 

 this for a fev/ feconds, and perceiving the appearance 

 frro A' more dark, and make a better defined impreffion on 

 The limb, I gave the fignal to the perfons who counted 

 time for me, which they noted down feparately at 2\ 12' 



3 



// 



by the clock. I fuppofe my telefcope might have fhewn 



■^ 1* 



the impreffion on the Sun's limb at leafl 15'' foonci 



'' When Venus was near one half of her diameter ad 

 vanced on the Sun, 1 faw diflinSly a border of light en- 

 compaffimg that part of her which was yet off the Sun, 

 This was'fo bright that it rendered that part of Venus 

 vifible and pretty well defined, although not yet entered on 



the 



* Mr. Rittcnhoufe thinks l:hat aperlbn who had feen titc Sun nearer the honK.on, and could 



u 



Rier fpkndor. " . , , , 



f I'hc obfervers with the rcfra^^orB were obliged to he on tiie ground^ wxtn their heads 



bolA'^rcd up by the perfons that ulFiUed them. 



I 



A 



J5 



V 



