Page images
PDF
EPUB

The Lion's barren, and no Vows can gain
The Maid; Aquarius spends his Youth in vain.
Ab! too remov’d, too far disjoin’d to prove

The fruitful Pleasures of encreasing Love ! Befides these, there are various other Distinctions made of the Signs, not one Jot less whimsical; as you will find in Manilius's second Book of his poetical Astronomy and Astrology. But leaving the Dreams and vain Imaginations of the Ancients, let us proceed to the Circles which remain.

Euphrof. With a very good Will, Cleonicus; let the little Time we have be spent to the Purpose; I had rather be possessed of a little Sterling Science, than all the Parade of trumpery Nonsense.

DIALOGUE VI.

[ocr errors]

Of the Colures, Tropics, POLAR-CIRCLES, and

the Poles of the World.

Cleonicus.
HE next Circles we are to consider, in the Sphere,

are those two called the Colures, both which pass through the Poles of the World, and cut the Equinoctial at right Angles.

Euphrof. And one of them passes thro' the Equinoctial Points, 1 obferve.

Cleon. It does so; and therefore it is called the Equi, noctial Colure; the other, which passes thro’ the Beginning of Cancer, is called the Solftitial Colure,

Euphrof. Whence hath it that Name?

Cleon. From hence, that when the Sun, in his annual Course, comes near to the Beginning of these Signs on either Side, he seems to move neither North, ward nor Southward for some Time, but as it were to be stationary, which Standing still of the Sun, is in the Latin called Solftitium, whence these two Points are called the Solstices,

[ocr errors]

Euphrof. What Distinction is made of these Solftitial Points ?

Cleon. Because the Sun, when it is in the Beginning of Cancer makes Midsummer, that Point is called the Summer Solstice; thus the other Point is called the Winter Solfice; because, when the Sun is in it, it is then Mid-winter.

Euphrof. And have not the other Points, which you call the Equinoxes, in which the other Colure cuts the Ecliptic, some distinct Denomination from the Seasons also ?

Cleon. Yes; for when the Sun is in the Beginning of Aries, it is then the Middle of the Spring, which in Latin is called Ver, and therefore this Equinox is called the Vernal Equinox; and when the Sun is in the other Equinox, it is the Middle of Autumn, which therefore is called the Autumnal Equinox.

Euphrof. Then these two Colures, I perceive, are, in a Sort, the Boundaries of the Seasons.

Cleon. That is their Office; they each of them point out two opposite Seasons by their two opposite Parts upon the Ecliptic. And these are the two most notable Meridians of those that are fixed; and the Solstitial Colure has this in particular, that it also passes through the Poles of the Ecliptic, and therefore cuts it also at right Angles. Of these Circles Manilius has given us this general Description.

From Pole all round to Pole two Lines express’d,
Adversely drawn, which inter feet the Reft,
And one another : They surround the whole,
And crofing, make right Angles at each Pole.
These into four just Parts divide the Sphere,

And mark by Signs the Seasons of the Year.
After this, he gives us a particular Description of each
Colure, and their Course through the various Constella-
tions of the Heavens: And first of the Equinoctial Colure

One drawn from Heav'n's bigh Top, defcends from fur,
And cuts the Serpent's Tail, and the dry Bear :
The Equinoctial Scales, the Snake's Extremes,
And next the Southern Centaur's middle Beams;
Then thwarts the adverse Pole, and next divides
The mighty Whale, and parts its scaly Sides.
Bright Aries Point, and splendid Trigon past
The fair Andromeda below the Wait ;

[ocr errors]

And next her Mother's Head it cuts, and then

The Pole, and closeth in itself again.
Then of the Solftitial Colure

Cross this, and from the Pole doth first appear
The other, through the Fore-feet of the Bear,
And through its Neck; which, when the Sun retires,
Firs fines, and spreads black Night, with feeble Fires,
Then parts the Twins and Crab, the Dog divides,
And Agro's Heel that broke the frothy Tides.
And then the Pole, and other Circle croll,
To Caper turns, contracted in his Frojt:
The Eagle cuts, and the inverted Lyre,
Black Draco's Folds-
The hinder Paws oth' Bear, and near the Pole
Its Tail; and closing there compleats the Whole.
These Rounds immoveable, their Site the fame,
Here Seafons fix, nor vary in the Frame.

Lib. I. Thus much, at present, is sufficient concerning the Colures ; let me now proceed to the Tropics.

Euphrof. Why are those two Circles called the Tropics, Cleonicus?

Cleon. To understand the Reason thereof nicely, you must know, (which you will easily observe) that while the Sun is going froin Aries to Cancer, he advances every Day more Northward than before he was, till being come to Cancer, he is most northerly that he can be; after which, as he descends to Libra, he gets ever Day more Southward than before. Now, when he is in the Beginning of Cancer, it is, that he changes his Motion, and turns from going Northward to go Southward : Now this Turning back of the Sun was by the Greeks called Trope; from whence the Parallel pafling through the Beginning of Cancer is called the Tropic of Cancer.

Euphros. Very good, I understand you well; and I see also the fame Reason, why the other is called the Tropic of Capricorn, because there the Sun returns from the southerly Course to his northern one. But, pray, what is reprelinted by these Tropics on the Sphere ?

Cleon. These Tropics represent (for any Latitude) the longeji and fortest Days in the Year ; for they shew the Part of the diurnal Motion of the Sun, for the two Days when he is in the Beginning of Cancer and Capricorn; where he has the greatest and least Meridian Altitude; and consequently, when he is in the first Minute of Cancer, all that Part of the Tropic of Cancer, which is above the Horizon, represents the Length of that Day; and all that is beneath the Horizon, represents the Night of that Day; and it is easy to observe, from the Sphere, that the Day is the longest, and that Night the shortest of all others in the Year. In the same Manner, the two Parts of the Tropic of Capricorn, above and below the Horizon, shew the shortest Day and longest Night in the Year.

Euphrof. I believe I apprehend your Meaning tolerably well, but you must make some Grains of Allowance to a Novice in these Studies.- Pray, have chese Tropics any other Use?

Cleon. They are the Boundaries between the Torrid and Temperate Zones on the terrestrial Globe, of which more hereafter. The Tropic of Cancer is thus poetically described by Manilius :

The Line describ'd through Cancer's Claws confines
The utmos Limits of the fatal Signs ;
There, when the Sun ascends his greatest Height,
In largest Rounds he whirls the Day and Night;
Pleas'd with his Station, there be seems to stay,

Nor lengthens much nor much contracts the Day.
And the Tropic of Capricorn, thus;

Another, Southward drawn, exactly sets
The utmost Limits to the Sun's Retreats;
When hoary Winter calls his Beams away,
Obliquely warms us with a feeble Ray,
And whirls, in narrow Rounds, the freezing Day.
To us his Journey's fort, but where he stands,
With Ray direct he burns the barren Sands.
To wish'd-for Night be scarce resigns the Day,
But in vast Heats extends his hated Sway.

Lib. I. We are now come to the Polar Circles, which are the last to be considered on the Sphere.

Euphrof. These, I remember, you told me were called the Aretic and Antarctic Circles ; pray, whence do they derive these Names ?

}

Cleon. The Aretic Circle, or that about the North Pole, is so called from Aretus, the Greek Name of the Constellation of the greater Bear, which is situated very near it; and the North Pole is sometimes called the Aritic Pole, because it is the last Star in the Tail of the lesier Bear ; as I shall shew you hereafter, when we come to discourse of the Constellations. The other is called the Antarctic Circle, as being on the opposite Part of the Sphere to this.

Euphrof. What is the Use of these Circles ?

Cleon. They shew the Latitude on each Side the Equinoctial, where the Sun does not let, or go below the Horizon, when he is at the greatest Distance, North and South, that is, in the Beginning of Cancer and Capricorn.

Euphrof. Indeed! is there such a Thing as all Day, and no Night, in that Latitude ?

Cleon. Yes; and the nearer you go from the Polar Circle to the Pole, the longer the Sun continues above the Horizon ; and precisely under the Pole, the Sun sets not for the Space of fix Months, or half a Year, as I shall demonstrate to you on the Globes hercafter; and the other half Year it is all Night; that is, the Sun is not seen from that Pole above the Horizon, which in that Case is the Equator itself.

Euphrof. This is very wonderful ; I hope I fall understand you better upon the Globes. But what other Use do you make of these Circles ?

Čleon. They are the Boundaries between the Temperate and Frigid Zones. These Circles also Manilius thus defcribes :

One tow'rds the North sustains the shining Bear,
And lies divided from the Polar Star
Twice twelve Degrees, and thirty Minures lefs;

Which Space the Tropics from the Line poless.
The Antaretic thus

The laft, drawn round the Southern Pole confines
Those Bears, and lie, the utmost of the Lines..
Wife Nature constant in her Work is found,

Wide as the Arctic is th' Antarctic Round. Euphros. But before we leave this Subject, pray tell me one Thing; why are the Ends of the Axis of the Sphere called the POLES of the World? Cleon. The Word Pole is Greek, and significs to turn

round

1

« PreviousContinue »