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\ 
LV. An Account of a Memoir Yead at the 
Royal Academy of Sciences at Paris, by 
M. de Barros, a Portuguefe Gentleman , 
concerning certain Phcenojnena obferved by 
him at Paris, in the lajl T*ranfit o/'Mercury 
over the Sun : by J. Short, A . M. F.R.S. 
\ 
Read Dec. 13, fT^HE author fays, he made ufe of 
I753 ' an excellent Gregorian refledtor 
of four feet in length, taking in the eye-piece, toge- 
ther with as much of the great tube, as exceeds the 
focal lengths of the two eye -glades (/ fuppofe it fhould 
be the two fpeculums ) : that the focus of the great 
fpeculumis33 [Paris) inches; that of the fmall one 
four inches j the focus of the eye-glafs next the eye 
1 8 lines 3 the focus of the glafs furtheft from the eye 
5 inches ; and, laftly, that the combined power of 
thefe two glafies is nearly equal to that of a fingle 
eye-glafs of 3 inches. This telefcope, therefore, ac- 
cording to my computation, magnified about 130 
times. 
That he was placed in the mod; commodious fitu- 
ation for obferving the egrels ; that his fmoaked glafs 
was fixed perpendicular to the axis of his telefcope 
within a clofe tube j and that he always made ufe of 
the fame part of this glafs. 
He took notice, that the interior contact of Mer- 
cury's and the Sun’s limbs * was very rapid, having 
obferved it with a green-colour’d glafs held over the 
Z z fmoaked 
* At io h 18’ 41 ' . 
