lax; and from his observations of which he deduced the important discovery of the Aberration of Light.

Let us now suppose that we are to contemplate the northern part of the heavens about the beginning of April, at ten o'clock in the evening. Turning our faces towards the Polestar, or directly north, and holding that part of the map uppermost which is opposite to the beginning of April, those stars which are marked on the upper part of the map will appear not far from the zenith, or nearly overhead; those towards the lower part will appear at a low elevation, not far from the horizon; those on the right will appear in the east, and those on the left in the west, at different elevations, as here represented. The two pointers in the Great Bear, which are directly opposite to the 1st of April, will be seen nearly in the zenith, and to point downward to the Pole-star; and, at nearly an equal distance below the Pole-star, they direct the eye to the constellation Cassiopeia, which is conceived to have a certain resemblance to a chair, and which appears only a small distance above the northern horizon. To the west or left-hand side of Cassiopeia is the constellation Perseus, of which Algenib is the principal star, and which is likewise at a low elevation. To the right, or east side of Cassiopeia, is Cepheus; four stars of which, two of the third and two of the fourth magnitude, form a kind of square, or rhombus. The stars farther to the east, and in a more elevated position, belong chiefly to the constellation of Draco, or the Dragon. The star Etanim, in this constellation, appears nearly due east of the Pole-star, at the distance of forty degrees. stars on the western side of the map, or on the left hand, nearly opposite to Etanim, belong to the constellation of Auriga; and those on the upper part are chiefly some of the prominent stars connected with the Great Bear. The bright star Capella appears nearly west by south from the Pole-star, at a pretty high elevation, with Menkalina a little above it, and to the eastward.

The

Besides the stars marked on the map, there may be seen, at the same time, several brilliant stars of the first magnitude. Turning the eye east by south, the bright star Arcturus, in the constellation Bootes, is seen about half way between the horizon and the zenith. Looking to the northeast, the brilliant star Vega, or Lyra, appears elevated twenty degrees above the horizon, in a direction nearly opposite to Capella,

in the west. Farther to the north, but not quite so elevated as Lyra, is Deneb, in the constellation of the Swan. Turning our eye to the west, Castor and Pollux will be seen about midway between the western horizon and the zenith; and farther down, near the horizon, almost due west, are Betelguese and Bellatrix, the two stars in the shoulders of Orion, Betelguese appearing the more elevated of the two, the other portions of Orion having descended below the horizon. To the southwest, midway between Pollux and the horizon, is Procyon, a star of the first magnitude in the Lesser Dog.

Suppose, now, we were to observe the same quarter of the heavens, at the same hour, about the beginning of October. In this case we have only to reverse the map, so that the first of October may be uppermost. At this season, Cassiopeia will appear near the zenith, and the two pointers of Ursa Major will be seen at the opposite side of the pole, at no great elevation above the horizon. Capella will appear towards the east, on the right, at a considerable altitude, and the five stars in the head of Draco considerably to the west, while Algenib, and the other stars in Perseus, will be seen in a high elevation, to the east of Cassiopeia. At this time, likewise, by turning our eyes towards the east and the south, Aldebaran, or the Bull's-eye, in the constellation Taurus, will be seen elevated about twelve degrees above the eastern horizon, about sixteen degrees above which are the Pleiades, or seven stars. The star Altair will appear near the southwest, half way between that point and the meridian, and Fomalhaut, in the Southern Fish, will be seen nearly on the meridian, only five or six degrees above the south point of the horizon.

In like manner, were we wishing to observe the position of the circumpolar stars at any other hour, at this period, than ten o'clock P.M., suppose at eight in the evening, we have only to turn the line which marks the beginning of September uppermost instead of October, and the position at that hour will be seen; and if we choose to make our observations at six in the evening, we turn the first of August to the top, allowing two hours, at an average, for every month. If we would inspect their position at twelve midnight, the first of November must be turned round to the top, and so on for any other hour. If we would make our observations in the beginning of January, at ten P.M., that point must be turned to the top, and then the two pointers will be seen on the right,

straight east from the Pole-star, and the other five stars hanging down from them, Cassiopeia nearly straight west, and Capella not far from the zenith. These circumpolar stars may therefore be seen at every season of the year, and their relative positions determined beforehand by simply turning round the map to the month, or day of the month, required, so that that point may be at the top; and although the months are arranged so as to correspond with ten o'clock P.M., yet the positions may be represented for any other hour, according to the directions given above.

The following remarks may be stated in reference to the stars depicted on this map: 1. All these stars never set in our latitude, but appear to move round above the horizon in circles, of which the pole is the centre. As the observer is supposed to be in fifty-two degrees N. latitude, all the stars within 52° of the pole never descend below the horizon. In one part of their diurnal course they appear above the pole, and some of them near the zenith, and in the opposite point they appear below the polar point, and sometimes near the northern horizon. 2. In the higher part of their course they appear to move from east to west, and in the lower part from west to east. Those nearest the pole describe small circles around the polar point, and those at greater distances describe larger circles; but their periods of apparent revolution are exactly the same, namely, twenty-three hours, fifty-six minutes, and four seconds. 3. The stars represented in this map are only those which are most prominent and obvious to the naked eye, in order to prevent confusion, and that the untutored observer may not be distracted with too many objects at one view. They chiefly consist of stars of the second, third, and fourth magnitudes. 4. In order that the observer may be able readily to estimate the apparent distances of the stars from each other and from the horizon, it may be proper to keep in mind that the distance between the two pointers is exactly five degrees, and between Dubbe (the nearest to the pole) and the Pole-star, twenty-nine degrees. By applying these measures by the eye to other stars, their apparent distances may be very nearly estimated. 5. Although I have stated, in general terms, that the pointers come to the southern meridian, or are nearly in the zenith, at ten P.M., about the beginning of April, yet it is not before the seventh of this month that they are accurately in this position at ten in the evening; but the differ

ence is not much perceptible by the eye during the course of a week or two, and therefore can lead to no great mistake. 6. If the circle containing the stars were cut out, and surrounded with the circle of months and days, and made to revolve within the circle of hours, it might be made to serve the purpose of an astronomical clock for pointing out the hours of the night, and likewise for showing the positions of the circumpolar stars for any hour of the day or night. 7. The delineations of the apparent distances of the stars on this map are on a scale of only one half the size of that on which the two preceding maps were constructed.

The three preceding views of certain portions of the heavens, partly delineated from actual observation, are intended to convey to general observers a natural representation of those quarters of the firmament to which they refer, so that by a little farther attention and observation, and an inspection of a celestial atlas, they may acquire a general view of the principal stars and constellations visible in our hemisphere; for on most celestial planispheres and globes there is such a group of eyes, noses, legs, tails, claws, and wings connected with the mythological figures of the constellations, no traces of which can be seen in the heavens, that the learner is sometimes confounded, and can scarcely trace any resemblance between what is depicted on such globes and planispheres and the real aspect of the firmament, the stars appearing, in many instances, as accidental spots, buried, as it were, amid the group of hieroglyphics with which they are connected.

CHAPTER II.

ON THE ARRANGEMENT OF THE STARS INTO CONSTELLATIONS, WITH SKETCHES OF THEIR MYTHOLOGICAL HISTORY.

In order to distinguish the stars from one another, the ancients divided the heavens into different portions or spaces, called constellations, or groups of stars. They supposed each group to occupy a space which a lion, a bear, a man, a harp, or other object would fill if it were there delineated; and