By beginning at its northernmost part, represented at the upper part of Plate XIII., situated in "the chair" of the constellation Cassiopeia, and descending southwardly, and continuing in the same direction until the whole circle is completed, the course of the Milky-way through the constellations may be briefly described as follows: From Cassiopeia's chair, the Galaxy, forming two streams, descends south, passing partly through Lacerta on the left, and Cepheus on the right; at this last point it approaches nearest to the polar star. Then it enters Cygnus, where it becomes very complicated and bright, and where several large cloudy masses are seen terminating its left branch, which passes to the right, near the bright star Deneb, the leader of this constellation. Below Deneb, the Galaxy is apparently disconnected and separated from the northern part by a narrow, irregular dark gap. From this rupture, the Milky-way divides into two great streams separated by an irregular dark rift. An immense branch extends to the right, which, after having formed an important luminous mass between the stars _γ_ and _β_, continues its southward progress through parts of Lyra, Vulpecula, Hercules, Aquila and Ophiuchus, where it gradually terminates a few degrees south of the equator. The main stream on the left, after having formed a bright mass around _ε_ Cygni, passes through Vulpecula and then Aquila, where it crosses the equinoctial just below the star _η_ after having involved in its nebulosity the bright star Altair, the leader of Aquila. In the southern hemisphere the Galaxy becomes very complicated and forms a succession of very bright, irregular masses, the upper one being in Scutum Sobieskii, while the others are respectively situated in Sagittarius and in Scorpio; the last, just a little above our horizon, being always considerably dimmed by vapors. From Scutum Sobieskii, the Galaxy expands considerably on the right, and sends a branch into Scorpio, in which the fiery red star Antares is somewhat involved. Continuing its course below our horizon, the Milky-way enters Ara and Norma, and then, passing partly through Circinus, Centaurus and Musca, it reaches the Southern Cross, after having been divided by the large dark pear-shaped spot known to navigators as the "Coal-Sack." In Ara and Crux the Milky-way attains its maximum of brightness, which there surpasses its brightest parts in Cygnus. In Musca, it makes its nearest approach to the south pole of the heavens. It then enters Carina and Vela, where it spreads out like a fan, and terminates in this last constellation, before reaching _λ_, being once more interrupted by a dark and very irregular gap, on a line with the two stars _γ_ and _λ_. It is noteworthy that this second rupture of continuity of the Galaxy in Vela is very nearly opposite, or at about 180° from the break near Deneb in Cygnus.