Page 87
The Position of the Sphaere,
IN respect to the Horizon, 'tis found that the Sphaere is constituted into a threefold Posi∣tion; As First, into a direct Sphaere; Secondly, into a Parallel Sphaere; and Thirdly, into an Ob∣lique Sphaere.
A Direct Sphaere hath both the Poles in the Horizon, and the Aequinoctial transiting the Ze∣nith. [ 10] In a Direct Sphaere all the Circles Parallel. to the Aequator make right Angles with the Ho∣rizon, and are also divided into two equal parts, by the Horizon; and in a Direct Sphaere the Sun, Moon, and Stars are always 12 Hours above the Horizon, and 12 Hours under it, and so by con∣sequenee make 12 Hours Days, and 12 Hours Night.
It is called a Direct Sphaere, because all the Celestial Bodies, as the Sun, Moon, and Stars, [ 02] viz. by the Diurnal Motion of the Primum Mo∣bile ascend directly above, and descend directly below the Horizon.
Those that Inhabit under the Aequator have the Sphaere thus posited, as in the Isle of St. Thomas, Sumatra, Bor∣neo, Celebes, a great part of Africa, and America. A, is the South Pole. [ 30] B, is the North Pole. A B, is the Horizon. C D, the Aequinoctial. E F, the Tropick of Cancer.
G H, the Tropick of Capricorn.
The Space betwixt G C, C E, and H D, D F, are the Parallels that the Sun describes in making his Revolution. The Arches under the Horizon A B, are the Night Arches, and those above it [ 40] the Day Arches.
A Parallel Sphaere hath one Pole of the World in the Zenith, the other in the Nadir, and the Equinoctial Line in the Horizon.
In a Parallel Sphaere all the Circles that are Parallel to the Equinoctial, are also Parallel to the Horizon; and in a Parallel Sphaere from the 10th of March to the 11th of September (the Sun being then in the Northern Signs, and conse∣quently on the North side of the Hemisphaere) there are six Months Day in the North, and six [ 50] Months Night in the South; and on the contrary, from the 11th of September to the 10th of March (the Sun being then in the Southernly Signs, and by consequence on the South-side of the Horizon) there are six Month Day in the South, and six Months Night in the North.
It is called a Parallel Sphaere, because the Sun, Moon, or Stars, in the Diurnal Revolution of the Heavens neither ascend, or descend, but always move Parallel to the Horizon. [ 60]
That is, When one of the Poles is in the Zenith, and the other in the Nadir, and that the Aequator is Parallel to the Horizon; as in this Figure, which shews how the Earth is posited to those suppo∣sed to dwell under the Pole.
An Oblique Sphaere hath the Axis of the World, neither Direct, nor Parallel to the Horizon. but lies slopwise from it.
In an Oblique Sphaere all the Celestial Bodies, as the Sun, Moon, Stars, &c. have (in respect of the Horizon) oblique and unequal Ascensions and Descensions, and all the Lines Parallel to the Aequator make unequal Angles with the Horizon, and are cut by the Horizon into unequal parts; for those Lines towards the Elevated Pole have a greater proportion of a Circle under the Horizon, than above it; only the Aequator, because it hath the same Center with the Horizon, doth di∣vide the Horizon into two equal parts, and is also divided into two equal parts by the Hori∣zon.
According to which it follows, that when the Sun is in any part of the Ecliptick that declines towards the elevated Pole, the Days in the ele∣vated Hemisphaere shall be longer than the Nights, and when the Sun is in any part of the Eclipstick that declines towards the depressed Pole, the Nights shall be longer than the Days; but when the Sun is in the Aequinoctial (because whether the Pole be raised, or depressed) equal proportions remain both above, and under the Horizon; therefore the Days are of the same length with the Nights, and the Nights with the Days.
Also in an Oblique Sphaere all those Stars that have as great, or greater number of Degrees of Declination, than is the elevated Poles Complement of Latitude to 90, never set, nor come under the Horizon; and those Stars that have the same Declination above the depressed Pole, never rise.
It is called an Oblique Sphaere, because all the Circles of the Sphaere move Obliquely above the Horizon. The Earth is thus oblique∣ly posited to all those Nations that Inhabit under any Degree of Latitude, either North or Southwards, be∣tween the Aequator and either Pole, as may be seen by this Fi∣gure.