( 4 ) 
As to the other part of the Argument, that the alte- 
ration of the declination of Sirius, on the (core of the 
accefs of the Earth in December, and its recefs in June, 
amounts to 6 Seconds; I can only remark, that, befides 
that a Radius of 3 Feet, as it feems that made ufe of 
was no more, is fomewhat too fmall for fo extremely 
nice an Obfervation, 6' being fubcended by the ~ 
(part of an Inch, fome of the Obfervations before recited 
do plainly (hew, that the Re fraction of the Medium did 
intermix with thofe Differences that might be occafioned 
•by the Parallax • 
But the principal Objection againfl the Conclufion 
of this Argument, feems to be, that the Meridian al- 
titude of Sirius at Paris being under xy Degrees, the 
ordinary Refra&ion of the Star is i' yy" or ny Se- 
conds ; and the Barometer rifing and falling above two 
Inches in Thirty, (hews that the denjity of the Air, on that 
(core, may be a ryth part more at one time than ano- 
ther. Whence the Refractions being always proportional 
to the denjity of the Medium , as we have all feen it often 
demonftrated by Mr. Hanksbee, both in F^acuo, and in a 
aoubly^nd trebly condenfed Air , it is plain that in that Al- 
titude the Refradion of a Star may differ about 7 or 8 
Seconds, or theiyth part of uy", which is more than 
the whole Parallax fuppofed to have been obferved. 
It were to be wifti’d that Mr. Cajfini would pleafe 
to try this Matter by the Lucida Lyr <e t inftead of £/- 
tins, which, tho’ fomewhat lefs than him, is as near to 
the SoQitial Colure , and has much greater Latitude, be- 
ing but 28 grad . from the Pole of the Ecliptick , whence 
its Parallax would be fo much greater ; and being at 
Paris within 10 grad, of the Zenith, the grand Obje- 
ction of the difference of Refradion, would be almoft 
wholly removed. 
If. An 
