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from bcing disbrdered in the Intervals of the Observations ; and diseoverat once, both that there is a Parallax, and that the Fixed Stars areat different Distances from us ; wherein, that I be not mistaken, mymcaning is not that the Instrument or Micrometer sliouJd bc rcmovedfor the observing of the Leffer Star, buc that (when the Azimuth ofthe grcater Star is taken ) by a Micronieter (confifting of divers sineThreads Parallel and Transverse) may ( at the (äme thue) be obfer'vcdthe Distance of the two Stars, each from otber, in that Position ( bothbcing at once within the reach of the Micrometer; ) which Distance(the Instrument remaining unmoved) if k be found (at disterent timesof the year) not to be the sime, this will prove that there is a diffe-rent Parallax of thesc two Stars.

This latter part of the Observation, ( of their different Distances atdifferent Times ) I loggest, as more casily practicable thougli not so Niccas the former. For it may be done, I think, without any further Ap-fpamtus there tlian a good Telelcope of ordinäry Form, furnistied witlia Micrometer, (this being carefully kept unvaried during the Intervalof theso Observations.) And if this part only of the Observation(without the other ) be purfued ; it matters not though the two Ob-lervations (near the two Solstices ) bc, or.e at the Lastern, the otherat the Western Azimuth (whcreby both may be taken in the Night time )for the Distance must ( at both Azimudrs ) be the sime. If after observingthe Azimuth of the greater Star it bc necestary to move the Micrometer forMeasoring its Distance from Alcor, that may be done another Night, (andit is not necestary to be done at one Observation) for that Distance cannot bediscernably varied in a Night or two.

X. Since the Pythngorcan Syßcm of the World has been revired by C.o-peniicus, (and now by all Mathematicians acceptcd for the True one)there seemed ground to imagine, that the Diameter of the Earth’s AnnualCourse (which according to our best Astronomers, is at least 40000 timesbigger than the Semidiaincter of the Earth) might give a Sensible Parallaxto the Fixt Stars, and thereby determine their Distance. But there aresome Considcrarions which make us sülpeci tliat even this Basis is not largeenough for tlrat purposo.

M. Huge»s ( who is very exact in bis Astronomical Observations)teils us, He could never discover any visible Magnitude in the FixtStars, though he used Glasles which magnihed the Apparent Diameterabove 100 times.

Now, since in all likelihood the Fixt Stars are Suns, (perhaps of adifferent Magnitude) we may as a reasonable Medium prelüme they are ge-nerallv about the bigncls of our Sun.

\ r ol. I. H h Ixt

Conctrnittg ti 'Dift-incc of tfixt Sturz ; I\{r. Fr. Ro-berts.

n. 20 f. /. 1 r