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TIGE TT 
MATHEMATICAL PAPERS. 115 
limbs of the fun and Mercury exa&ly coincided. I therefore 
:ftimated the internal contaé by the firft appearance of a fmall 
threailof. light between them. | This took placeat 10% 12/7, 
The elliptical appearance was then wholly gone, and Mercury 
appeared circular, and perfectly well-defined. But the tremu- 
lous motion of the fun’s limb was then fo great, that this obíer- 
vation feemed. picsdeict Viam: "uncertainty of eight or. 
ten feconds.. — 
When Mercury was wholly within the fun, I applied myfelf 
to the micrometer to meafure the diameters: of the fun and Mer- 
cury, and.the leaft diftance of their limbs.. By a mean of eight 
obfervations taken. during- the tranfit, I found the fin; s hori- 
zontal diameter to. be 32' 21,85 :. This was-the fame with 
he ref e lt of Eval file, phfereitions- goes. a. b lire. intor 
ameter of rre L madot dee sane E 
times during the tranfit.. The greateft care was taken to have - 
them accurate : And the mean of. all the pepe gi son 
