reprefent the convex Face of the Heavens, the Spectator muft either fuppofe himself placed. above the Stars, or elfe carry his imagination fo far as to conceive the Stars which are placed on the right fide of the figure in the Map, to be view'd on the left fide in the Heavens, and likewife thofe that are on the left fide in the Map, to be view'd on the right fide in the Heavens; and that the Planets or Stars which feem to move from Eaft to Weft, or from the left to the right, by their diurnal motion, when they are placed right before them, must move on thofe Maps on the contrary; that is, from Weft to Eaft, or from the right to the left. And as the Planets themselves, in their revolutions thro' their Orbs, appear to move from Weft to Eaft, or from the right to the left, must here be traced (on the contrary) from Eaft to Weft, or from the left to the right; a thing, that to Perfons not very converfant in thefe Matters, occafions very often fome difficulty.

As the Ecliptick and its feveral Parallels of Latitude are all drawn by a Scale, it contributes very much to the readier difcovering of what Stars the Moon (or any of the Planets) will pafs by, or cover in any of their revolutions thro' their Orbs; and the Parallels of Declination being all drawn as before, it may be discover'd at fight what Stars will tranfit the Meridian, at or near the fame altitude with the Moon, or any other Planet or fixed Star: And in as much as in this cafe they are all fubject to the fame refraction, and the Errors of the Inftruments made ufe of (if any there be) being alike in all, does not a little contribute to the

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readier finding of the Declination of any unknown Star or Planet at that time, by getting rid of fome uncertainties, that otherwife Obfervations of this kind would be liable to.

§. IX. Connection of the Atlas now published, with the Hiftoria Coeleftis, publish'd fome years ago.

That the Reader may be the better enabled to know the names of the feveral Stars, and distinguish them one from the other, there are Letters annex'd to the principal Stars in each Map, which refer to the Catalogue printed in the 3d Volume of the Hiftoria Cæleftis; where, in the proper Conftellations, he will find against the referential Letters, the Name, right Afcenfions, Declination, Latitude, Longitude, &c. of each particular Star.

And here the mutual Connection and Relation opening, in which the prefent Work ftands to that other of the Hiftoria Cæleftis Britannica of the fame Author; it may not be amifs, becaufe of the ftrict alliance, and mutual light they caft upon one another, here to prefent the Reader with a fhort and fummary Account of the faid Work; efpecially fince (tho' but lately publish'd) no account has as yet been given of it in this Journal: Tho' in the narrow Limits we are here confin'd to, this can scarce amount to any more than a mere Index, or a bare Enumeration of the principal Contents of this noble Work. Which take as follows.

ARTICLE II.

HISTORIA Cœleftis Britannica, Tribus Voluminibus contenta. Auctore JoANNE FLAMSTEDIO, Aftronomo Regio.

That is,

THE Britannick Aftronomical HISTORY of the Heavens, in Three Volumes, Fol. By the late Reverend Mr. FLAMSTED, Aftron. Prof. Reg.

TH

HE firft Volume contains the Obfervations of Mr. William Gascoigne, (the first Inventor of the way of measuring Angles in a Telescope by the help of Screws, and the firft that applied Telescopical Sights to Aftronomical Inftruments) taken at Middleton near Leeds in Yorkshire, betwixt the years 1638 and 1643; extracted from his Letters to Mr. Crabtree : With fome of Mr. Crabtree's Obfervations in the fame years; as alfo Obfervations of the Sun's and Moon's Diameters; Configurations and Elongations of Jupiter's Satellits from him, finall diftances of fixed Stars, with appulfes of the Moon and Planets to them; obferved with

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a Telescope and Micrometer at Derby, by Mr. Flamfted, betwixt the years 1670 and 1675, with the larger intermutual Distances of fixed Stars, and of the Planets from them; Eclipfes of the Sun, Moon, and Jupiter's Satellites ; Spots on the Sun, Comets, and Refractions, taken with a Sextant of near feven foot Radius, a valuable Quadrant, and the abovemention'd Inftruments, betwixt the years 1675 and 1689, at his Majefty's Obfervatory, rang'd under proper heads; with the places of the Moon, Saturn, Jupiter, Mars, Venus and Mercury, deduced from the Obfervations; and alfo neceffary Tables to be used with them.

The fecond Volume contains his Obfervations (made with a mural arch of near feven foot Radius, and 140 degrees the Limb) of the meridional zenith Distances of the fixed Stars, Sun, Moon, and other Planets, with the time of their tranfits over the Meridian: Together with Obfervations of the Sun's and Moon's Diameters; Eclipfes of the Sun, Moon, and Jupiter's Satellites; Variations of the Compafs, from 1689 to the end of the year 1619, &c.

Tables, fhewing how to render the Calculation of the Stars and Planets places, from the Obfervations, eafy and expeditious: To which are added, the places of the Moon, (at the Oppofitions, Quadratures, and on her Limits, &c.) and the places of Saturn, Jupiter, Mars, Venus and Mercury, derived from the abovementioned Obfervations.

The third Volume contains a Catalogue of the right Afcenfions, Diftances from the Pole, Longitudes and Magnitudes of near 3000 fixed Stars

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Stars; with the variations of their right Afcenfions and Distances from the Pole, whilft they change their Longitude one degree, whereby their right Afcenfions and Distances from the Pole may be determined, for 200 years past or to come, fufficiently exact. Large Tables, by which the right Afcenfions and Distances from the Pole of the Stars and Planets being given, their Longitudes and Latitudes may be found by inspection.

To this Volume is prefixed a very large and curious Preface; containing an account of all the aftronomical Obfervations made before his own time; with a particular Defcription of the Inftruments made ufe of for this purpose, in all the feveral different Ages and Countries of the World; as alfo a very ample and full account of his own Obfervations and Inftruments, and their advantage and fuperiority above any before used by the Aftronomers. Together with a new Latin verfion of Ptolemy's Catalogue of 1026 fix'd Stars, from the Greek, and Uleg-beig's places annex'd on the Latin page, with the corrections: As alfo fmall Catalogues of the Arabs; Tycho Brahe's Catalogue of about 780 fix'd Stars, in a proper order: The Landgrave of Heffe's Catalogue of 386 fix'd Stars: Hevelius's Catalogue of 1534, in a proper order. order. A Catalogue of fome of the Southern fix'd Stars, not visible in our Hemisphere, reduced to right Afcenfion, Distance from the Pole, Longitude and Latitude; with variations of right Afcenfions and Distances from the Pole: Calculated from Obfervations made by Dr. Halley at St. Helena; and Mr. Flamfted's Stars places, and fitted to the year 1726.