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tic ocean, the Streights of Belleisle, New Britain, the noiih part of the province of Canada, New South Wales, the southern part of Kamschatka; thence over different Tartarian nations, several provinces of Russia, over Poland, part of Germany, the southern part of the United Provinces; then, crossing the sea, it arrives again in the meridian of London.
When the sakl star, or any other star, is on the meridian of London, or any other meridian, all other stars, according to their declination and right ascension, and difference of right ascension (which answers to terrestrial latitude, longitude, and difference of longitude), will, at the same time, be on such meridians, and vertical to such places as correspond in latitude, longitude, and difference of longitude, with the declination, &c. of the respective stars.* >
From the stars, therefore, thus considered, we attain a copious field of geographical knowledge, and may gain a clear idea of the proportionable distances, and real bearings, of remote empires, kingdom*, and provinces, from our own zenith, at the same instant of time; which may be found in the same manner as we found the place to which the sun was vertical at any proposed time.
Many instances of this mode of attaining geographical knowledge, may be found in my father's treatise on the globes.
* Fait-maii's Geography.
OF THE USE OF THE CELESTIAL GLOBE, IN PROBLEMS RELATIVE TO THE PLANETS.
The situation of the fixed stars being always the same with respect to one another, they have their proper places assigned to them on the globe.
But to the planets no certain place can be assigned, their situation always varying.
That space in the heavens, within the compass of which the planets appear, is called the zodiac.
The latitude of the planets scarce ever exceeding 8 degrees, the zodiac is said to reach about 8 degrees on each side the ecliptic.
Upon the celestial globe, on each side of the ecliptic, are drawn eight parallel circles, at the distance of one degree from each other, including a space of 16 degrees; these are crossed at right angles, with segments of great circles at every 5 th degree of the ecliptic; by these, the place of a planet on the globe, on any given day, may be ascertained with accuracy.
Problem Xxxviii. Tofind the. place of any planet upon the globe, and by that means to find its place in the heavens, also, to find at what hour any planet will rise or set, or be on the meridian, on any day in the year'.
Rectify the globe to the latitude and sun's place, then find the planet's longitude and latitude in an ephemeris, and set the graduated -edge of the moveable meridian to the given longitude in the ecliptic, and counting so many degrees amongst the parallels in the zodiac, either above or below the ecliptic, as her latitude is north or south; and set the centre of the artificial sun to that point, and the centre willrepresent the place of the planet for that time.
Or fix the quadrant of altitude over the pole of the ecliptic, and holding the globe fast, bring the edge of the quadrant to cut the given degree of longitude on the ecliptic; then seek the given latitude on the quadrant, and the place under it is the point sought
While the globe moves about its axis, this point moving along with it will represent the planet's motion in the heavens. If the planet be brought to the eastern side of the horizon, the horary index will shew the time of its rising. If the artificial sun is above the horizon, the planet will not be visible: when the planet is under the strong brass meridian, the hour index shews the time it will be on that circle in the heavens : when it is at the western edge, the time of its setting will be obtained.
Problem xxxix. To Jind directly the planets which are above the horizon at sun-set, upon any given day or latitude.
Find the sun's place for the given day, bring it to the meridian, set the hour index to XII, and elevate the pole for the given latitude: then bring the place
s 36*8 'PROBLEMS.
of the sun to the western semicircle of the horizon, and observe what signs are in that part of the ecliptic above the horizon, then cast your eye upon the ephemeris for that month, and you will at once see what planets possess any of those elevated signs; for such will be visible, and fit for observation on the night of that day.
Problem Xl. Tojind the right ascension, declination, amplitude, azimuth, altitude, hour of the night, Sgc. of any given planet, for a day of a month and latitude given.
Rectify the globe for the given latitude and day of the month; then find the planet's place, as before directed, and then the right ascension, declination, amplitude, azimuth, altitude, hour, &c. are all found, as directed in the problems for the sun; there being no difference in the process, no repetition can be necessary.
OF THE USE OF THE CELESTIAL GLOBE, IN PRO-, BLEMS RELATIVE TO THE MOON.
From the sun and planets we now proceed to those problems that concern the moon, the brilliant satellite of our earth, which every month enriches it with its presence; by the mildness of its light softening the darkness of night; by its influence affecting the tide ; and by the variety of its aspects, bffering to our view some very remarkable phenomena
<! Soon as the ev'ning shades prevail^
As the orbit of the moon is constantly varying in its position, and the place of the node always changing, as her motion is even variable in every part of her orbit, the solutions of the problems which relate to her, are not altogether so simple as those which concern the sun.
The moon increases her longitude in the ecliptic every day about 13 deg. 1O min. by which means she crosses the meridian of any place about 50 min. later than she did the preceding day.
Thus, if on any day at noon her place (longitude) be in the 12th deg. of Taurus, it will be 13 deg. 10 min. more, or 25 deg. 10 min. in Taurus on the succeeding noon.
It is new-moon when the sun and moon have the sairfe longitude, or are in or near the same point of the ecliptic.
When they have opposite longitudes, or are in opposite points of the ecliptic, it is full-moon.
To ascertain the moon's place with accuracy, we must recur to an ephemeris; but as even- in most