PLATE V. contains a condensed representation of some of the principal constellations in the northern and southern hemispheres on Mercator's Projection, chiefly for the purpose of exhibiting THE COURSE OF THE MILKY WAY, and the relative positions of the constellations. Some of the larger stars may be here traced, as a Lyræ, Capella, &c., but they are more easily distinguished in the other maps. (See the description given of the course of the Milky Way, p. 144.)

Fig. 80 (p. 340) represents the comet of 1661, as seen by Hevelius; the atmosphere, or nebulosity surrounding the nucleus, when viewed at different times, varied in its extent, as likewise the tail in its length and breadth.

Fig. 81 (p. 340) represents a class of comets which have their tails somewhat bent, which some suppose to be owing to the resistance of the ethereal fluid through which they move.

Fig. 85 represents a telescopic view of the Pleiades, a group of stars in the constellation Taurus. About forty stars are here represented, but with powerful telescopes many more may be discovered. Rheita affirms that he counted 200 stars within this cluster, and yet telescopes, at the period when he lived, had not arrived at the point of perfection they have now attained. The principal star in the Pleiades is Alcione, of the third magnitude, which is here represented near the centre of the cluster. The names of the others visible to the naked eye are Merope, Maia, Electra, Tayeta, Sterope, and Celino. Merope is the one which some suppose to have been lost. In fabulous history these stars were the seven daughters of Atlas and the nymph Pleione, who were turned into stars, with their sisters the Hyades, on account of their mutual affection and amiable virtues.

The other five stars, besides Alcione, are of the fifth magnitude, as represented in the plate; and the rest are telescopic stars of the sixth, seventh, eighth, and ninth magnitudes. The lines from right to left are portions of circles of declination, which run parallel with the equinoctial, as the parallels of latitude on the terrestrial globe do with respect to the equator; and on these the declination, or distance of the body from the equinoctial, is marked. The other lines, from top to bottom, are portions of circles of right ascension corresponding with meridians on the terrestrial globe. On these are marked the right ascensions of the heavenly bodies or their distance, reckoned on the equinoctial from the first point of Aries.

One of these lines, at the top and bottom, is marked 54°, showing that the stars in that line are 54° east from the first point of Aries; and the number 23, marked at the right and left hand sides, shows that the star or stars in that line are 23° north of the equinoctial.

Fig. 86 represents the tail of the splendid comet of 1744, which was divided into six branches, as described p. 349. See also the description given of this comet, p. 332, 333.