( ? ) 
appear’d equal to the Diameter of the Star, which he 
cakes to be five, or at moil fix Seconds. 
Suppofing this to be fo, he then (hews that the whole 
Diameter of the annual Orb is to the diflance of £/- 
yius, as the Sine of 6" to the Sine of 39 0 3 3 the Lati* 
tude of the Star, whence the aforefaid immenfe mag- 
nitude of the Body thereof, is a neceflary Confequence. 
But before this obtain a full alTent, it may not per- 
haps be amifs to enquire whether the (uppos’d vifible 
Diameter of Sirius , were not an Optick Fallacy, occafi- 
oned by the great contra&ion of the aperture of the Ob» 
jeftGlafs: For we all know that the Diameters of AU 
debar an and Spica Virginis , are fo fmall, that when they 
happen to immerge on the dark Limb of the Moon , 
they are fo far from loofing their Light gradually, as 
they muft do were they of any fenfible magnitude, that 
they vanifh at once with their utmoft Luftre ; and 
emerge likewife in a Moment, not fmall at firft, buc at 
once appear with their full Light, even tho’ the Emerfi-* 
on happen very near the Cujp 5 where, if they were four 
Seconds in Diameter, they would be many Seconds of 
Time in getting entirely feparated from the Limb. But 
the contrary appears to all thofe, that have oblerved 
the Occultations of thefe bright Stars. And tho 5 Sirius 
be bigger than either of them, yet he is by far lefs 
than two of them ; and consequently his Diameter to 
theirs is lefs than the Square Root of 1 to 1, or than 
iq to 10; whence, in Mr. Cajfinis excellent 36 Foot 
Glafs, thofe Stars ought to be about four Seconds in 
Diameter ; and they would undoubtedly appear fo, if 
view’d alter the fame manner; whereas we are aliunde 
certain, that they are lefs than one fingle Second in 
Diameter. The great ftrength of their native Light, 
forming the refemblance of a Body, when it is nothing 
elfe buc the fpilfuude of their Rays. 
