Chapter II: Part 2

Made and Sold by RICHARD CUSHEE _at the Globe and Sun between St. Dunstans Church & Chancery Lane and_ Tho:Wright _Instrument-maker to His Majesty at the Orrery and Globe near Salisbury Court_

FLEET STREET LONDON

ESTATES Survey’d _ALSO_ MAPS _DRAWN_ and _ENGRAV’D_]

[Sidenote: The distribution of the Stars into 6 classes.]

[Sidenote: Of _Telescopical Stars_.]

The astronomers distribute the Stars into several orders or classes; those that are nearest to us, and appear brightest to the eye, are called Stars of the first magnitude; those that are nearest to them in brightness and lustre, are called Stars of the second magnitude; those of the third class, are stiled Stars of the third magnitude; and so on, until we come to the Stars of the sixth magnitude, which are the smallest that can be discerned by the naked eye. There are infinite numbers of smaller Stars, that can be seen through telescopes; but these are not reduced to any of the six orders, and are only called _Telescopical Stars_. It may be here observed, that tho’ the astronomers have reduced all the Stars that are visible to the naked eye, into some one or other of these classes, yet we are not to conclude from thence that all the Stars answer exactly to some or other of these orders; but there may be in reality as many orders of the Stars, as they are in number, few of them appearing exactly of the same bigness and lustre.

[Sidenote: The Stars digested into constellations]

The ancient astronomers, that they might distinguish the Stars, in regard to their situation and position to each other, divided the whole starry firmament into Several _Asterisms_, or systems of Stars, consisting of those that are near to one another. These _Asterisms_ are called _Constellations_, and are digested into the forms of some animals; as Men, Lyons, Bears, Serpents, _&c._ or to the images of some known things; as, of a Crown, a Harp, a Triangle, _&c._

[Sidenote: _Zodiac._]

The starry firmament was divided by the ancients into 48 images, or constellations; twelve of which they placed in that part of the Heavens wherein are the planes of the Planetary orbits; which part is called the _Zodiac_, because most of the constellations placed therein resemble some living creature. The two regions of the Heavens that are on each side of the _Zodiac_, are called the North and South parts of the Heavens.

[Sidenote: Constellations within the Zodiac.]

The constellations within the _Zodiac_ are, 1. _Aries_, the _Ram_; 2. _Taurus_, the _Bull_; 3. _Gemini_, the _Twins_; 4. _Cancer_, the _Crab_; 5. _Leo_, the _Lion_; 6. _Virgo_, the _Virgin_; 7. _Libra_, the _Balance_; 8. _Scorpio_, the _Scorpion_; 9. _Sagittarius_, the _Archer_; 10. _Capricornus_, the _Goat_; 11. _Aquarius_, the _Water-Bearer_; and, 12. _Pisces_, the _Fishes_.

[Sidenote: Northern constellations.]

The constellations on the North side of the _Zodiac_ are Twenty-one, _viz._ the _Little Bear_; the _Great Bear_; the _Dragon_; _Cepheus_, a king of _Ethiopia_; _Bootes_, the keeper of the _Bear_; the _Northern Crown_; _Hercules_ with his Club, watching the _Dragon_; the _Harp_; the _Swan_; _Cassiopeia_; _Persius_; _Andromeda_; the _Triangle_; _Auriga_; _Pegasus_, or the _Flying Horse_; _Equuleus_; the _Dolphin_; the _Arrow_; the _Eagle_; _Serpentarius_; and the _Serpent_.

[Sidenote: Southern constellations.]

The constellations noted by the ancients on the South side of the _Zodiac_, were fifteen, _viz._ the _Whale_; the river _Eridanus_; the _Hare_; _Orion_; the _Great Dog_; _Little Dog_; the Ship _Argo_; _Hydra_; the _Centaur_; the _Cup_; the _Crow_; the _Wolf_; the _Altar_; the _Southern Crown_; and the _Southern Fish_. To these have been lately added the following, _viz._ The _Phœnix_; the _Crane_; the _Peacock_; the _Indian_; the _Bird of Paradise_; the _Southern Triangle_; the _Fly_; _Cameleon_; the _Flying Fish_; _Toucan_, or the _American Goose_; the _Water Serpent_, and the _Sword Fish_. The ancients placed those particular constellations or figures in the Heavens, either to commemorate the deeds of some great man, or some notable exploit or action; or else took them from the fables of their religion, _&c_. And the modern astronomers do still retain them, to avoid the confusion that would arise by making new ones, when they compare the modern observations with the old ones.

[Sidenote: _Unformed Stars._]

Some of the principal Stars have particular names given them, as _Syrius_, _Arcturus_, _&c._ There are also several Stars that are not reduced into constellations, and these are called _Unformed Stars_.

[Sidenote: The _Galaxy_, or _Milky Way_.]

Besides the Stars visible to the naked eye, there is a very remarkable space in the Heavens, called the _Galaxy_, or _Milky Way_. This is a broad circle of a whitish hue, like milk, going quite round the whole Heavens, and consisting of an infinite number of small Stars, visible thro’ a telescope, tho’ not discernable by the naked eye, by reason of their exceeding faintness; yet with their light they combine to illustrate that part of the Heavens where they are, and to cause that shining whiteness.

The places of the fixed Stars, or their relative situations one from another, have been carefully observed by astronomers, and digested into catalogues. The first among the _Greeks_, who reduced the Stars into a catalogue, was _Hypparchus_, who, from his own observations, and of those who lived before him, inserted 1022 Stars into his catalogue, about 120 years before the Christian _Æra_: This catalogue has been since enlarged and improved by several learned men, to the number of 3000, of which there are a great many telescopical, and not to be discerned by the naked eye; and these are all ranked in the catalogue as the Stars of the seventh magnitude.

It may seem strange to some, that there are no more than this number of Stars visible to the naked eye; for sometimes in a clear night they seem to be innumerable: but this is only a deception of our sight, arising from their vehement sparkling, while we look upon them confusedly, without reducing them into any order; for there can seldom be seen above 1000 Stars in the whole Heavens with the naked eye at the same time; and if we should distinctly view them, we shall not find many but what are inserted upon a good _Celestial_ Globe.

Altho’ the number of Stars that can be discerned by the naked eye are so few, yet it is probable there are many more which are beyond the reach of our optics, for through telescopes they appear in vast multitudes, every where dispersed throughout the whole Heaven; and the better our glasses are, the more of them we still discover. The ingenious Dr. _Hook_ has observed 78 Stars in the _Pleiades_, of which the naked eye is never able to discern above 7; and in _Orion_, which has but 80 Stars in the _British_ catalogue (and some of them telescopical) there has been numbered 2000 Stars.

[Sidenote: An idea of the Universe.]

Those who think that all these glorious bodies were created for no other purpose than to give us a little dim light, must entertain a very slender idea of the Divine Wisdom; for we receive more light from the _Moon_ itself, than from all the _Stars_ put together. And since the _Planets_ are subject to the same laws of motion with our _Earth_, and some of them not only equal, but vastly exceed it in magnitude, it is not unreasonable to suppose, that they are all habitable Worlds. And since the _Fixed Stars_ are no ways behind our _Sun_, either in bigness or lustre, is it not probable, that each of them have a system of _Planetary Worlds_ turning round them, as we do round our Sun? And if we ascend as far as the smallest Star we can see, shall we not then discover innumerable more of these glorious bodies, which now are altogether invisible to us? And so _ad infinitum_, thro’ the boundless space of the universe. What a magnificient idea must this raise in us of the _Divine Being_! Who is every where, and at all times present, displaying his Divine Power, Wisdom and Goodness, amongst all his Creatures!

_The_ DESCRIPTION _and_ USE _of the_ CELESTIAL _and_ TERRESTRIAL GLOBES.

[Sidenote: _Globe_ or _Sphere_.]

A _Globe_ or _Sphere_ is a round solid body, having every part of its surface equally distant from a point within it, called its _Center_; and it may be conceived to be formed by the revolution of a semicircle round its diameter.

[Sidenote: _Great Circle._]

[Sidenote: _Hemispheres._]

Any circle passing through the center of the sphere, thereby dividing into two equal parts or segments, is called a _Great Circle_; and the segments of the sphere so divided, are called _Hemispheres_.

Every great circle has its Poles and Axis.

[Sidenote: _Poles._]

The _Poles_ of a great circle are two points on the surface of the sphere, diametrically opposite to one another, and every where equally distant from the said circle.

[Sidenote: _Axis._]

The _Axis_ of a circle is a right line passing through the center of the sphere, and through the Poles of the said circle, and is therefore perpendicular to the Plane: Therefore

[Sidenote: _Secundaries._]

All circles passing through the Poles of any great circle, intersect it in two places diametrically opposite, and also at right angles; and with respect to the said great circle, they may be called its _Secundaries_.

[Sidenote: _Parallel_ or _lesser Circles_.]

All circles dividing the sphere into two unequal parts, are called _lesser_ or _parallel Circles_, and are usually denominated by that great circle to which they are parallel.

[Sidenote: _Terrestrial Globe._]

The Earth being globular, its outward parts, as the several _Countries_, _Seas_, _&c._ are best, and most naturally represented upon the surfaces of a Globe; and when such a body has the outward parts of the Earth and Sea delineated upon its surface, and placed in their natural order and situation, it is called a _Terrestrial Globe_.

[Sidenote: _Celestial Globe._]

The Celestial Bodies appear to us as if they were all placed in the same concave sphere, therefore astronomers place the Stars according to their respective situations and magnitudes, and also the images of the constellations, upon the external surface of a Globe; for it answers the same purposes as if they were placed within a concave sphere, if we suppose the Globe to be transparent, and the eye placed in the center. A Globe having the Stars placed upon its surface, as above described, is called a _Celestial Globe_. These Globes are both placed in frames, with other appurtenances, as shall be described in a proper place.

[Sidenote: The principal use of the Globes.]

The principal uses of the Globes (besides their serving as _Maps_, to distinguish the outward parts of the Earth, and the situations of the fixed Stars) is to explain and resolve the phænomena arising from the diurnal motion of the Earth round its Axis.

[Sidenote: There will be the same prospect of the fixed Stars whether the spectator be placed on the Earth, or in the Sun.]

It has been shewed in the Introduction, that the distance of the Earth from the Sun, is no more than a point, when compared with the immense distance of the fixed Stars; therefore let the Earth be in what point soever of her orbit, there will be the same prospect of the Heavens, as a spectator would observe did he reside in the Sun: And if several circles be imagined to pass thro’ the center of the Earth, and others, parallel to them, be conceived to pass thro’ the center of the Sun, these circles in the Heavens will seem to coincide, and to pass exactly thro’ the same Stars. Wherefore as to the appearances of the fixed Stars, it is indifferent whether the Earth or the Sun be made the center of the Universe. But because it is from the Earth that we always observe the celestial bodies, and their apparent motions seem to us to be really made in the Heavens, it is more natural in explaining the phænomena arising from these motions, to place the Earth in the center. And again, because the semidiameter of the Earth, when compared to her distance from the Sun, is of no sensible magnitude, any point, upon the Earth’s surface, let her be in what part soever of the orbit, may be considered as being the center of the Universe. Upon these principles, the different phænomena arising from the diurnal motion of the Earth, and the different situation of a spectator upon its surface, are very naturally illustrated and explained by the Globes.

As to the alterations of seasons, _&c._ arising from the annual motion of the Earth round the Sun, it is indifferent which we suppose to move, the Earth or the Sun, for in both cases the effect will be the same. Wherefore because it is the Sun that appears to us to move, we say the Sun is in such a part of the ecliptic, without attributing any motion to the Earth, any more than if she had actually been at rest. For the same reason we say the Sun rises, or the Sun sets; by which we mean that he begins to appear or disappear, without considering in the least how these effects are produced. These things are here mentioned, to obviate the objections that might be made by beginners, after they have been told that the Sun stands still.

SECT. I.

_An Explanation of the Circles of the Sphere, and of
some Astronomical Terms arising therefrom._

[Sidenote: The _Circles of the Sphere_.]

In order to determine the relative situations of places upon the Earth, as well as the positions of the fixed Stars, and other Celestial phænomena, the Globe of the Earth is supposed to be environed by several imaginary circles, and these are called the _Circles of the Sphere_. These imaginary circles are either fixed, and always obtain the same position in the Heavens, or moveable, according to the position of the observer.

Those circles that are fixed, owe their origin to the two-fold motion of the Earth, and are the _Equator_, and the _Ecliptic_, with their _Secundaries_ and _Parallels._ These fixed circles are usually delineated upon the surface of the Globes.

The moveable circles are only the _Horizon_, its _Secundaries_ and _Parallels_: These are represented by the wooden frame, and the brass ring, wherein the Globe is hung, and a thin plate of brass to be screwed in a proper place, upon the said ring, as occasion requires.

I. _Of the Equinoctial._

[Sidenote: The _Equator_, or _Equinoctial_.]

1. The _Equator_, or the _Equinoctial_, is that great circle in the Heavens, in whose plane the Earth performs her diurnal motion round her axis; or it is that great circle, parallel to which the whole Heavens seem to turn round the Earth from East to West in 24 Hours.

_Note_, The Equator and the Equinoctial are generally synonymous terms; but sometimes the Equator particularly signifies that great circle upon the surface of the Earth, which coincides with the Equinoctial in the Heavens. This circle is also by Mariners commonly called the _Line_.

[Sidenote: _Northern_ and _Southern Hemispheres_.]

[Sidenote: _The Axis of the World._]

[Sidenote: _Poles of the World_, or _of the Equator_.]

The equinoctial divides the globe of the Earth, and also the whole Heavens into two equal parts, North and South, which are called the _Northern_ and _Southern Hemispheres_. The axis of this circle, is called the _Axis of the World_, or the _Earth’s Axis_, because the Earth revolves about it (from West to East) in 24 hours. The extreme of this axis are called the _Poles of the World_, whereof that which lies in the Northern Hemisphere, is called the _North Pole_, and the other is called the _South Pole_. The equinoctial circle is always delineated upon the surface of each globe, with its name at length expressed; the axis of this circle, or the Earth’s axis, is only an imaginary line in the Heavens, but on the globes it is expressed by the wires about which they really turn. The Poles of the world, are the two points upon the surface of the globe through which these wires pass; the North Pole is that which hath the little brass circle, with a moveable index placed round it; and the other opposite to it is the South Pole. The Northern Hemisphere is that wherein the North Pole is placed, and the opposite one is the Southern Hemisphere.

The astronomers divide all circles into 360 equal parts, called _Degrees_, each degree into 60 equal parts, called _Minutes_, each minute into 60 _Seconds_, &c. But besides this division into degrees, the equinoctial is also divided into 24 equal parts, or _Hours_, each hour into 60 _Minutes_, each minute into 60 _Seconds, &c._ so that one hour is equal to 15 degrees, each minute of time is equal to 15 minutes of a degree, _&c._

[Sidenote: _Hour Circles_ or _Circles of Ascension_, also called _Meridians_.]

2. All circles conceived to pass through the Poles of the world, intersecting the equinoctial at right angles, are, with respect to any point in the Heavens, called _Hour Circles_; and the _Circles of Ascension_, because the ascension of the Heavenly bodies, from a certain point, are by them determined.

These circles are also, with regard to places upon Earth, called _Meridians_.

[Sidenote: The _Brass Meridian_.]

The _Meridians_ are commonly drawn upon the Terrestrial Globe thro’ every 15 degrees of the equinoctial, thereby making an Hour difference betwixt the places through which they pass. On the Celestial Globe there are commonly drawn but two of these _Meridians_, crossing the equinoctial in four points equidistant from one another, thereby dividing it into four quadrants; but the intermediate ones are here supplied, and also upon the Terrestrial Globe, by the brass circle on which they are hung, which, is therefore called the _Brass Meridian_, and sometimes only the _Meridian_, it serving for this purpose to all the points upon either Globe.

[Sidenote: The _Hour Circle_.]

There is also a little brass circle fixed upon this meridian, divided into 24 Hours, having an index moveable round the axis of the globe, to be turned to any particular Hour. The use of this circle is to shew the difference of time betwixt any two meridians, and is therefore called the _Hour Circle_.

[Sidenote: _Parallels of Declination._]

3. All circles parallel to the equinoctial are, with respect to any point in the Heavens, called _Parallels of Declination_. So that,

[Sidenote: _Declination North_ and _South_.]

4. The _Declination of any Point_ in the Heavens (as of the _Sun_, a _fixed Star_, or the like) is an arch of the meridian passing through that point, and intercepted betwixt it and the equator; and if the said point be to the (Northward/Southward) of the equator, it is called (_North_/_South_) _Declination_.

[Sidenote: _Tropics_ and _Polar Circles_.]

Of the parallels of declination, four are eminently distinguished by particular names, _viz._ The two _Tropics_, and the two _Polar Circles_.

[Sidenote: _Tropic of Cancer; of Capricorn._]

The tropics are on different sides of the equator each 23 degrees and 29 minutes distant from it; that which lies in the Northern Hemisphere, is called the _Tropic of Cancer_, and the Southern one, the _Tropic of Capricorn_.

These circles are the limits of the Sun’s greatest declination, and are called tropics, because whenever the Sun arrives to them, he seems to return back again towards the equator.

[Sidenote: _Arctic Circle._]

[Sidenote: _Arctic Pole._]

[Sidenote: _Antarctic Circle._]

[Sidenote: _Antarctic Pole._]

6. The _Polar Circles_ are each of them at the same distance from the Poles of the world, that the tropics are from the equator, _viz._ 23° 29′. That which lies near the North Pole, is called the _Arctic Circle_, from _Arctos_, a constellation situated in the Heavens near that Place; whence also this Pole is sometimes called the _Arctic Pole_. The other Polar circle, which is situated near the South Pole; is called the _Antarctic Circle_, because its position is contrary to the other; and the South Pole is sometimes called the _Antarctic Pole_.

The tropics and the Polar circles have each their names expressed upon the Globes.

II. _Of the Ecliptic._

[Sidenote: _Ecliptic._]

[Sidenote: _Equinoctial._]

[Sidenote: _Solstitial Points._]

[Sidenote: _Colures._]

[Sidenote: _Equinoctial Colure._]

[Sidenote: _Solstitial Colure._]

7. The _Ecliptic_ is that great circle in whose plane the Earth performs its annual motion round the Sun; or, in which the Sun seems to move round the Earth, once in a year. This circle makes an angle with the equinoctial of 23 degrees 29 minutes, and intersects it in two opposite points, which are called the _Equinoctial Points_; and the two points in the ecliptic that are at the greatest distance from the equinoctial points, are called the _Solstitial Points_. The two meridians passing through those points, are, by way of eminence, called _Colures_; whereof that which passeth thro’ the equinoctial points, is called the _Equinoctial Colure_; and that which is at right angles to it, passing through the Solstitial Points, is called the _Solstitial Colure_.

[Sidenote: The Ecliptic divided into signs.]

The ecliptic is divided into 12 equal parts, called _Signs_, each sign being 30 degrees, beginning from one of the equinoctial points, and numbered from West to East; the names and characters of the twelve signs are as follows, _viz._

_Aries_, _Taurus_, _Gemini_, _Cancer_, _Leo_, _Virgo_,
1. ♈ 2. ♉ 3. ♊ 4. ♋ 5. ♌ 6. ♍
_Libra_, _Scorpio_, _Sagittarius_, _Capricornus_, _Aquaries_,
7. ♎ 8. ♏ 9. ♐ 10. ♑ 11. ♒
_Pisces_.
12. ♓

[Sidenote: _Northern Signs._]

The first six of these are called the _Northern Signs_, and possess that half of the ecliptic which is to the Northward of the equator; beginning with the first point of ♈, and ending with the last point of ♍.

[Sidenote: _Southern Signs._]

The latter six are called the _Southern Signs_, because they possess the Southern half of the ecliptic; beginning at the first point of ♎, and ending with the last point of ♓.

The division of the ecliptic into signs, and the names of the colures, are particularly expressed upon the globes.

The signs of the ecliptic took their names from 12 constellations mentioned in the Introduction to be situated in the Heavens near those places. It is to be observed, that the signs are not to be confounded with the constellations of the same name: For the _Sign of Aries_, is not the same with the _Constellation_ Aries; the latter is a system of Stars digested into the figure of a _Ram_, but the sign of _Aries_ is only 30 degrees of the ecliptic, counted from the equinoctial point ♈, (which is reckoned the first point in the ecliptic) to the beginning of _Taurus_: Or, it is sometimes taken for all that space upon the Celestial Globe contained between the two circles passing through the first points of ♈ and ♉. What has been here said of _Aries_, is to be noted of all the rest of the signs.

The constellations above-mentioned were formerly situated within the signs which now bear their names; but by a slow motion of the equinoctial points, being one degree in 72 years, the constellation _Aries_ has now got into the sign ♉, and so of the rest. So that _Pisces_ is now got into the Sign of ♈; this slow motion in the Heavens is called the _Precession of the Equinoctial Points_.

[Sidenote: _Poles of the Ecliptic._]

The _Poles of the Ecliptic_ are both situated in the Solstitial Colure, at 23 degrees, 29 minutes distance from the Pole of the world; and they take their denomination from the Hemisphere wherein they are placed, _viz._ that which lies in the (Northern/Southern) Hemisphere, is called the (North/South) Pole of the ecliptic. The arctic and antarctic circles, are described by the Poles of the ecliptic in the diurnal motion of the Earth round its axis, whence it seems these two circles are called _Polar_.

[Sidenote: _Circles of Longitude._]

8. All great circles passing through the Poles of the ecliptic, and consequently intersecting it at right angles, are called _Circles of Longitude_: So that,

[Sidenote: _Longitude of any Point in the Heavens._]

[Sidenote: _Place of a Star._]

9. The _Longitude_ of any _Point_ in the Heavens (as a _Star_ or _Planet_, _&c._) is an arch of the ecliptic contained between the circle of longitude passing thro’ that point, and the equinoctial point ♈. And that degree of any sign which lies under the circle of longitude, passing thro’ any Star or Planet, is called the _Place_ of that Star or Planet.

_Note_, The _Sun_ never goes out of the ecliptic, and it is not usual to say the Sun’s longitude, but we commonly express it the _Sun’s Place_, which is that sign, degree, minute, _&c._, of the ecliptic, which he at any time passes.

10. All circles conceived to be drawn parallel to the ecliptic, are called _Parallels of Latitude_: So that,

[Sidenote: _Latitude of a Star, &c._]

11. The _Latitude_ of any point in the Heavens, (as a fixed Star, _&c._) is an arch of the circle of longitude, in passing thro’ that point, and intercepted betwixt it, and the ecliptic; or, the latitude is the distance from the ecliptic; and if the said point be to the Northward of the ecliptic, it is called North Latitude; but if it be to the Southward, is called South Latitude.

Upon the _Terrestrial Globe_, none of the circles of longitude are described; and upon the _Celestial_, they are commonly drawn thro’ the beginning of every _Sign_; but they are all supplied upon both Globes, by fastening a thin plate of brass over one of the Poles of the ecliptic, and so as to be moved to any degree thereof at pleasure. The parallels of latitude are also supplied by the graduations upon the said plate, as shall be shewn in a proper place.

We have now done with all those circles that are fixed, and such as are drawn upon the Globes themselves; we next proceed to the moveable circles.

III. _Of the Horizon._

[Sidenote: _Horizon._]

12. The _Horizon_ is that great circle which divides the upper, or visible Hemisphere of the world, from the lower, or invisible: This circle is distinguished into two sorts, the _Sensible_, and the _Rational_.

[Sidenote: _Sensible Horizon._]

The _Sensible_, or _Apparent Horizon_, is that circle which limits or determinates our prospect, whether we are at land or sea, reaching as far as we can see, or it is that circle where the Sky and the Earth, or Water, seem to meet. When we are on _Terra Firma_, this circle commonly seems rugged and irregular, occasioned by the unevenness of the ground terminating our prospect; but at sea there are no such irregularities; the semidiameter of this circle varieth according to the height of the eye of the observer; if a man of six feet high stood upon a large plain, or the surface of the sea, he could not see above three miles round.

This circle determines the rising and setting of the Heavenly bodies, and distinguishes Day and Night.

[Sidenote: _Rational Horizon._]

The _Rational_, or true _Horizon_, is a great circle passing thro’ the center of the Earth, parallel to the sensible Horizon, being distant from it by the Earth’s semidiameter, which is about 3980 miles: This distance is nothing in comparison of the immense distance of the Sun and the fixed Stars, therefore astronomers make no distinction between these two circles, but consider the apparent Horizon, or that wherein the Sun appears to rise and set, as passing thro’ the center of the Earth.

[Sidenote: _Cardinal Points of the Horizon._]

This circle is divided by astronomers into four quadrants, and each of the quadrants into 90 degrees, _&c._ The four points quartering this circle are called the _Cardinal Points_, and are termed the _East_, _West_, _North_, and _South_. The _East_ is that point of the Horizon where the Sun rises when he is in the equinoctial, or on that day when he ascends above the Horizon exactly at six o’clock; and the _West_ is that point of the Horizon which is directly opposite to the East, or where the Sun Sets when he is in the Equinoctial. The _South_ is 90 degrees distant from the East and West, and is toward that part of the Heavens wherein the Sun always appears to us in _Great-Britain_ at Noon; and the _North_ is that part of the Heavens which is directly opposite to the South: Or, the North and South points of the Heavens may be found by turning yourself either directly towards the East or the West: If you look towards the (East/West) the (South/North) will be to the right Hand, and the (North/South) to the left.

[Sidenote: _Points of the Compass._]

Besides the aforementioned divisions of the Horizon into degrees. _Mariners_ divide it into 32 equal parts, which they call the _Points of the Compass_; to each of which points they give a particular name, compounded of the four Cardinals, according to what quarter of the Compass is intended.

[Sidenote: _Zenith._]

[Sidenote: _Nadir._]

The center of the Horizon is the place of observation, and the Poles of it are one exactly over our heads, called the _Zenith_; and the other exactly under our feet, called the _Nadir_.

[Sidenote: _Vertical Circles._]

[Sidenote: _Meridian._]

[Sidenote: _Azimuth._]

13. All circles conceived to pass thro’ the Zenith and Nadir, are called _Vertical Circles_, or _Azimuths_. Of these circles, that which passeth thro’ the North and South points of the Horizon, is called the _Meridian_; so that when any object is upon the Meridian, it then bears either due South, or due North from us; and the _Azimuth_ of any object is an arch of the Horizon intercepted between the vertical circle passing through it, and either the North or South part of the Meridian; which part is commonly specified.

The meridian passes thro’ the Poles of the world, as well as through the Zenith and Nadir, and therefore is a secundary both of the equinoctial and the horizon: This circle divides the globe into the _Eastern_ and _Western Hemispheres_, and the Poles of it are the _East_ and _West_ points of the _Horizon_. All the heavenly objects are, during one half of their continuance above the horizon, in the Eastern Hemisphere, and for the other half in the Western; so that whenever the Sun arrives upon the upper part of the meridian, it is then _Noon_, or _Mid-day_, which is the reason why this circle is called the meridian; and when he comes to the lower part, it is then _Midnight_.

[Sidenote: _Prime Vertical._]

The vertical circle passing thro’ the East and West points of the horizon, is called the _Prime Vertical_, or _Circle_ of _East_ and _West_, so that when any object is upon this circle in the Eastern hemisphere, it appears due East; and if it be in the Western hemisphere, it appears due West.

[Sidenote: _Amplitude._]

That degree in the horizon wherein any object rises or sets from the East or West points, is called the _Amplitude_; which for rising is called _Amplitude Ortive_, and _Occasive_ for setting; which must be also denominated whether it be Northerly or Southerly.

It may be observed, that the _Amplitude_ and _Azimuth_ are much the same; the amplitude shewing the bearing of any object when he rises or sets, from the East or West points of the horizon; and the azimuth, the bearing of any object when it is above the horizon, either from the North or South point thereof. As for example, if an object rises or sets within 10 degrees of the East or West, suppose towards the South, we accordingly say, its _Amplitude_ is 10 degrees Southerly; but if an object, that is of any height above the horizon, should be in the vertical circle, passing thro’ the before-mentioned point, we then say, its _Azimuth_ is 80 degrees from the South, or 100 degrees from the North, both which expressions signify the same.

[Sidenote: _Almacanthers._]

[Sidenote: _Altitudes._]

[Sidenote: _Meridian Altitude._]

[Sidenote: _Zenith Distance._]

14. All circles drawn parallel to the horizon, in the upper hemisphere, are called _Almacanthers_, or _Parallels of Altitude_: So that the _Altitude_ of any point in the Heavens is an arch of the vertical circle passing thro’ that point, and intercepted betwixt it and the horizon; and if the object be upon the meridian, it is commonly called the _Meridian Altitude_. The complement of the altitude, or what it wants of 90 degrees, is called the _Zenith Distance_.

The horizon (by which we mean the rational) is represented by the upper surface of the Wooden frame, wherein the globes are placed; upon this horizon are described several concentric circles, the innermost of which is divided into degrees, which ought to be numbered both ways from the East and the West, until they end at 90 degrees in the North and South points. The use of these divisions is to shew the amplitudes of the Sun and Stars, at their rising and setting: Also in some convenient place upon this horizon, there is commonly noted the points of the Compass. Without the before-mentioned circle there is drawn the ecliptic with its divisions, into signs, and degrees, and a circle of months and days: The use of these two circles is to serve as a kalendar to shew the Sun’s place at any time of the year, and by that means to find his place in the _Ecliptic_, drawn upon the globe itself.

The _Vertical Circles_, and the _Parallels of Altitude_, are supplied by a thin plate of brass, having a nut and screw at one end to fasten it to the brass meridian in the Zenith point; which being done, the lower end of it may be put between the globe it self, and the inner edge of the horizon, and so turned round about to any point required.

[Sidenote: _Quadrant of Altitude._]

The fiducial edge thereof representing the _Vertical Circles_, and the _Degrees_ upon it, describing the Parallels of Altitude. This thin plate is called the _Quadrant of Altitude_.

The center of the horizon being the place of observation, it is evident that this circle, and all the others belonging to it, are continually changed, which way soever we move; wherefore we may suppose the horizon, with its secundaries and parallels, to invest the globe like a _rete_ or net; and to be moveable every way round it. This is very naturally illustrated by the globes; if we move directly North, or directly South, the change made in the horizon, is represented by moving the brass meridian (keeping the globe from turning about its axis) in the notches made in the wooden horizon, just so much as we travelled. If our course should be due East, or due West, the alterations made thereby are represented by turning the globe accordingly about its axis, the brass meridian being kept fixed; and if we steer betwixt the meridian and the East or West points, then we are to turn the brass meridian, and also the globe about its axis accordingly; the sum of which is, let the spectator be at what point soever of the Earth’s surface, he’ll there gravitate, or tend exactly towards its center, and imagine himself to be on the highest part thereof, (the unevenness of the ground not being here considered) wherefore if we turn the globe in such a manner as to bring the several progressive steps of a traveller successively to the Zenith, we shall then have the successive alterations made in the horizon, in every part of his journey. This explication being well considered, will be of help to young beginners, to conceive how the Earth is every where habitable; and how passengers can travel quite round it; for since every thing tends toward the center of the Earth, we are to conceive that point as being the lowest, and not to carry our idea of downwards any farther. Those that are diametrically opposite to us being as much upon the upper part of the Earth as we are, there being no such thing in nature as one place being higher than another, but as it is at a greater distance from the center of the Earth, let it be in what country soever.

We have now done with all the circles of the sphere, and it may be observed, that the _Equinoctial_, the _Ecliptic_, and the _Horizon_, with their Secundaries and parallels, are all alike; and altering their position, may be made to serve for one another. Thus, if the _Poles of the World_ be brought into the _Zenith_ and _Nadir_, the _Equinoctial_ will coincide with the _Horizon_, the _Meridians_ will be the same with the _Vertical Circles_, and the parallels of _Declination_ will be the parallels of _Altitude_. After the same manner, if shifting the position, we bring the _Ecliptic_ to coincide with the _Horizon_, the circles of _Longitude_ will be the _Vertical Circles_, and the parallels of _Latitude_ and _Altitude_ will coincide.

The horizon and the equator may be either parallel, perpendicular, or oblique to each other.

[Sidenote: _Parallel Sphere._]

15. A _Parallel Sphere_ is that position where the equator coincides with the horizon, and consequently the poles of the world are in the Zenith and Nadir: The inhabitants of this sphere (if there be any) are those who live under the poles of the world.

[Sidenote: _Right Sphere._]

16. A _Right_ or _Direct Sphere_ is that position where the equator is perpendicular to the horizon, the inhabitants whereof are those who live under the equinoctial.

[Sidenote: _Oblique Sphere._]

17. An _Oblique Sphere_ is when the equinoctial and the horizon make oblique angles with each other, which every where happens but under the equator and the poles.

[Sidenote: _Diurnal_ and _Nocturnal Arch_.]

The arch of any parallel or declination, which stands above the horizon is called the _Diurnal Arch_; and the remaining part of it, which is below the horizon, is called the _Nocturnal Arch_.

That point of the equinoctial which comes to the (Eastern/Western) part of the horizon with any point of the Heavens, is called the (Ascension/Descension) of that point, counted from the beginning of ♈; and if it be in a right sphere, the ascension or descension is called right; but if it be an oblique sphere it is called an oblique ascension or descension. So that,

[Sidenote: _Right Ascension._]

18. The _Right Ascension_ of the _Sun_, _Moon_, or any _Star, &c._ is an arch of the equator contained betwixt the beginning of ♈, and that point of the equinoctial which rises with them in a _Right Sphere_, or which comes to the meridian with them in an oblique sphere.

[Sidenote: _Oblique Ascension._]

19. _Oblique Ascension_, or _Descension_, is an arch of the equinoctial intercepted between the beginning of ♈, and that _Point_ of the _Equator_ which rises or sets with any point in the Heavens in an oblique sphere.

[Sidenote: _Ascensional Difference._]

20. _Ascensional Difference_, is the difference betwixt the right and oblique ascension or descension, and shews how long the Sun rises or sets before or after the hour of six.

IV. _Of the Division of Time._

The parts that time is distinguished into, are _Days_, _Hours_, _Weeks_, _Months_, and _Years_.

A Day is either natural or artificial.

[Sidenote: _Natural_ and _Artificial Day_.]

A _Natural Day_ is the space of time elapsed while the Sun goes from any meridian or horary circle, ’till he arrives to the same again; or, it is the time contained from noon, or any particular hour, to the next noon, or the same hour again: An _Artificial Day_ is the time betwixt the Sun’s rising and setting; to which is opposed the _Night_, that is, the time the Sun is hid under the horizon.

[Sidenote: _Hours_, &c.]

[Sidenote: _Equinoxes._]

[Sidenote: _Vernal_ and _Autumnal Equinox_.]

[Sidenote: _Solstices._]

[Sidenote: _Summer_ and _Winter Solstices_.]

The _Natural Day_ is divided into 24 _Hours_, each hour into 60 _Minutes_, each minute into 60 _Seconds, &c._ The _Artificial Days_ are always unequal to all the inhabitants that are not under the equator, except when the Sun is in the equinoctial points ♈ and ♋, which happens (according to our way of reckoning) about the 21st of _March_, and the 23d of _September_; at those times the Sun rises at six and sets at six to all the inhabitants of the Earth. These days are called the _Equinoxes_, or _Equinoctial Days_; the first of which, or when the Sun is in the first point of _Aries_, is called the _Vernal Equinox_, and the latter is called the _Autumnal Equinox_. In all places where the Sun descends below the horizon, excepting under the equator, the days continually lengthen or shorten, and that faster or slower, according as the Sun is nearer to, or further from the equinoctial, until he arrives to either of the _Solstitial Points_ ♋ or ♑. At those times the Sun seems to stand still for a few days, and then begins to return with a slow motion towards the equinoctial, still hastening his pace as he comes nearer to it: The Sun enters the tropics of ♋ and ♑, about the 21st of _June_, and the 22d of _December_, which days are sometimes called the _Solstices_; the first of which we call the _Summer Solstice_, and the latter the _Winter Solstice_.

[Sidenote: The different beginning of the day.]

All nations do not begin their day, and reckon their hours alike. In _Great-Britain_. _France_, and _Spain_, and in most places in _Europe_, the days is reckoned to begin at midnight, from whence is counted twelve hours ’till noon, then twelve hours more ’till next midnight, which makes a compleat day; yet the _Astronomers_ (in these countries) commonly begin their day at noon, and so reckon 24 hours ’till next noon, and not twice twelve, according to the vulgar computation.

[Sidenote: _Babylonish Hours._]

[Sidenote: _Italian Hours._]

The _Babylonians_ began their day at Sun-rising, and reckoned 24 hours ’till he rose again! This way of computation we call the _Babylonish Hours_. In several parts of _Germany_ they count their hours from Sun-setting, calling the first hour after the Sun has set, the first hour, _&c._ ’till he sets the next day, which they call the 24th hour: These are commonly called the _Italian Hours_. According to both these ways of computation, their hours are commonly either a little greater or less than the ¹/₂₄ part of a natural day, in proportion as the Sun rises or sets sooner or later in the succeeding days. They have also this inconvenience, that their mid-day and midnight happen on different hours, according to the seasons of the year.

[Sidenote: _Jewish Hours._]

[Sidenote: _Planetary Hours._]

The _Jews_ and the _Romans_ formerly divided the artificial days and nights each into 12 equal parts; these are termed the _Jewish Hours_, and are of different lengths, according to the seasons of the year; a _Jewish Hour_ in summer being longer than one in winter, and a night-hour shorter. This method of computation is now in use among the _Turks_, and the hours are stiled the _first hour_, _second hour, &c._ of the day or night; so that _Mid-day_ always falls on the sixth hour of the day. These hours are also called _Planetary Hours_, because in every hour one of the seven Planets were suppose to preside over the World, and so take it by turns. The first hour after Sun-rising on _Sunday_ was allotted to the _Sun_; the next to _Venus_, the third to _Mercury_; and the rest in order to the _Moon_, _Saturn_, _Jupiter_, and _Mars_. By this means on the first hour of the next day, the Moon presided, and so gave the name to that day; and so seven days by this method had names given them from the Planets that were supposed to govern on the first hour.

[Sidenote: _A Week._]

A _Week_ is a system of seven days, in which each day is distinguished by a different name. In most countries these days are called after the names of the seven Planets, as above noted. All nations that have any notion of religion, lay apart one day in seven for public worship; the day solemnized by _Christians_ is _Sunday_, or the first day of the week, being that on which our saviour rose from the grave, on which the apostles afterwards used more particularly to assemble together to perform divine worship. The _Jews_ observed _Saturday_, or the seventh day of the week, for their sabbath, or day of rest, being that appointed in the fourth commandment under the Law. The _Turks_ perform their religious ceremonies on _Friday_.

[Sidenote: _A Month._]

[Sidenote: _Periodical_ and _Synodical Month_.]

A _Month_ is properly a certain space of time measured by the Moon in his course round the Earth. A _Lunar Month_ is either _Periodical_ or _Synodical_. A _Periodical Month_ is that space of time the Moon takes to perform her course from one point in the ecliptic ’till she arrives to the same again, which is 27 days, and some odd hours; and a _Synodical Month_ is the time betwixt one new Moon, and the next new Moon, which is commonly about 29½ days. But a _Civil Month_, is different from these, and consists of a certain number of days, fewer or more, according to the laws and customs of the country where they are observed.

[Sidenote: A _Year Sydereal_ and _Tropical_.]

The compleatest period of time is a _Year_, in which all the variety of seasons return, and afterwards begin anew. A _Year_ is either _Astronomical_ or _Civil_. An _Astronomical Year_ is either a _Sydereal_ wherein the Sun departing from a fixed Star, returns to it again; or _Tropical_, which is the space of time the Sun takes to perform his course from any point of the ecliptic, ’till he returns to it again.

A _Tropical Year_ consists of 365 days, 5 hours, and 49 minutes; this is the time in which all the seasons compleatly returns, which is a small matter less than a Sydereal Year.

[Sidenote: _Egyptian Year._]

The _Civil Year_ is the same with the _Political_ established with the laws of a country; and is either moveable or immoveable. The moveable year consists of 365 days, being less than the tropical year by almost six hours, and is called the _Egyptian Year_, because observed in that Country.

The _Romans_ divided the year into 12 kalendar months, to which they gave particular names, and are still retained by most of the _European_ nations, _viz. January_, _February_, _March_, _April_, _May_, _June_, _July_, _August_, _September_, _October_, _November_, and _December_. The number of days in each month may be known by the following verses:

_Thirty Days hath_ September,
April, June, _and_ November;
February _hath Twenty-eight alone_,
_And all the rest have Thirty-one_.

The year is also divided into four quarters or seasons, _viz._ _Spring_, _Summer_, _Autumn_, and _Winter_. These quarters are properly made when the Sun enters into the equinoctial and solstitial points of the ecliptic; but in civil uses they are differently reckoned, according to the customs of several countries. In _England_, we commonly reckon the first day of _January_ to be the first in the year, which is therefore vulgarly called _New-Year’s-Day_; but in political and ecclesiastical affairs, the year is reckoned to commence on _Lady-day_ which is the 25th of _March_; and from thence to _Midsummer-day_, which is the 24th of _June_, is reckoned the first quarter; from _Midsummer-day_ to _Michaelmas-day_, which is the 29th of _September_, is the second quarter; the third quarter is reckoned from _Michaelmas-day_ to _Christmas-day_, which is the 25th of _December_; and from _Christmas-day_ to _Lady-day_, is reckoned the last quarter in the year. In common affairs, a quarter is reckoned from a certain day to the same in the fourth month following. Sometimes a month is reckoned four weeks, or 28 days, and so a quarter 12 weeks. To all the inhabitants in the (Northern/Southern) Hemisphere, their _Midsummer_ is properly when the Sun is in the tropic of (_Cancer_,/_Capricorn_,) and their _Midwinter_ at the opposite time of the year; but those who live under the equinoctial have two winters, _&c._ when the Sun is in either tropic; tho’ indeed properly, there is no season that may be called winter in those parts of the world.

[Sidenote: _Bissextile_, or _Leap-Year_.]

The _Egyptian_ year of 365 days being less than the true solar year, by almost six hours, it follows, that four such years are less than four solar years by a whole day; and therefore in 365 times four years, that is, in 1460 years, the beginning of the years move through all the seasons. To remedy this inconveniency, _Julius Cæsar_ (considering that the six hours, which remain at the end of every year, will in four years make a natural day) ordered that every fourth year should have an intercalary day, which therefore consists of 366 days; the day added was put in the month of _February_, by postponing St. _Matthias_’s day, which in common years fall on the 24th, to the 25th of the said month, all the fixed feasts in the year from thenceforwards falling a week-day later than otherwise they would. According to the _Roman_ way of reckoning, the 24th of _February_ was the sixth of the kalends of _March_, and it was ordered that for this year there should be two sixths, or that the sixth of the kalends of _March_ should be twice repeated; upon which account the year was called _Bissextile_, which we now call the _Leap-Year_.

To find whether the year of our Lord be leap-year, or the first, second, or third after; divide it by four, and the remainder, if there be any, shews how many years it is after leap-year; but if there be no remainder, then that year is leap-year: Or, you may omit the hundreds and scores, and divide the residue by 4, _Examp._ 1757, omitting the hundreds and the twenties, I divide the residue 17, by 4, and the remainder 1, shews it to be the first after leap-year.

[Sidenote: _Julian Account_ or _the Old Style_.]

This method of reckoning the year, _viz._ making the common year to consist of 365 days, and every fourth year to have 366 days, is now used in _Great-Britain_ and _Ireland_, and some of the Northern parts of _Europe_, and is called the _Julian Account_, or the _Old Style_. But the time appointed by _Julius Cæsar_ for the length of a solar year is too much; for the Sun finishes his course in the ecliptic, in 365 days, 5 hours, and 49 minutes, which is 11 minutes less than the civil year; and therefore he again begins his circuit 11 minutes before the civil year is ended; and so much being gained every year, amounts in 131 years, to a whole day. So that if the Sun in any year entered the equinox upon the 20th of _March_ at noon, after the space of 131 years, he’ll enter the same point on the same hour, on the 19th of _March_. And therefore the exquinoxes will not always fall on the same day of the month, but by degrees will move towards the beginning of the year.

[Sidenote: _Gregorian Account_, or _New Style_.]

At the time of the _Council of Nice_, when the terms were settled for observing of _Easter_, the _Vernal Equinox_ fell upon the 21st of _March_; but by its falling backwards 11 minutes every year, it was found that in _Anno_ 1582, when the kalendar was corrected, the Sun entered the equinoctial circle on the 11th of _March_, having departed ten whole days from its former place in the year: and therefore Pope _Gregory_ the XIIIth, designing to place the equinoxes in their situation with respect to the year, took these ten days out of the kalendar, and ordered that the 11th of _March_ should be reckoned as the twenty-first: And to prevent the seasons of the year from going backwards for the future, he ordered every hundredth year, which in _Julian_ form was to be a _Bissextile_, should be a common year, and consist only of 365 days; but that being too much, every fourth hundred was to remain _Bissextile_. This form of reckoning being established by the authority of Pope _Gregory_ XIII. is called the _Gregorian Account_, or the _New Style_; and is observed in all the countries where the authority of the Pope is acknowledged, and likewise by several nations of the reformed religion. There being now above an hundred years past, since the reformation was made in the kalendar, the _Gregorian_ account has accordingly got before the _Julian_ one day more than it was in the time of its institution, the difference between these two accounts being now eleven days; so that the first day of any month, according to that way of reckoning, is the 12th of the same month, according to the New Style.

I shall conclude this section with a brief account of the Atmosphere.

[Sidenote: _Atmosphere._]