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LXXVIII. A Propofal for difcovering the 
Annual Parallax of Sirius ; by the Rev. 
Nevil Mafkelyne, A. M. Fellow of Tri- 
nity College } Cambridge, and F. R. S . 
Read June 26 , f ^ HE Royal Society having come to 
fl a refolution to fend perfons of abi- 
lity to proper places, in order to obferve the ap- 
proaching palfage of Venus over the Sun, the 6th of 
June next year 5 (which phenomenon was firfl pro- 
pofed to this Society, by the late excellent Dr. Hal- 
ley, forty-four years ago, as a proper means of de- 
termining the Sun’s parallax, to a great degree of 
exadnefs) I take this opportunity of recommending 
to the confideration of this learned body another 
very important objed in aftronomy, which, I appre- 
hend, may be cleared up at the fame time, by the 
aftronomers fent to one of thofe places, which will 
probably be judged convenient for the obfervation of 
Venus’s tranfit; I mean the ifland of St. Helena. 
The aftronomical objed, in favour of which I de- 
fire to engage your attention, is no lefs than the de- 
termination of the annual parallax of the Orbis 
Magnus j the finding out of which, from obferva- 
tion, would be the fulled: and diredeft proof of the 
Copernican fyffem, as the want of this proof, hi- 
therto, has been the ftrongeft argument made ufe of 
by thofe, who have with-held their alfent to an hy- 
pothecs, which fo fully, and yet limply, fatisfies all 
the other phenomena. 
No 
