Part 6
8. A _Climate_ is a tract of the surface of the Earth, included between two such parallels of latitude, that the length of the longest day in the one exceeds that in the other by half an hour.
The whole surface of the Earth is considered, as being divided into 60 climates, _viz._ from the equator to each of the polar circles 24, arising from the difference of ½ hour in the length of their longest days; and from the polar circles to the Poles themselves, are six, arising from the difference of an entire month, the Sun being seen in the first of these a whole month without setting; in the second two; and in the third, three months, _&c._ These climates continually decrease in breadth, the farther they are from the equator. How they are framed, _viz._ the parallel of latitude in which they end (that being likewise the beginning of the next) with the respective breadth of each of them, is shewed in the following table:
_A_ TABLE _of the_ CLIMATES.
CLIMATES _between the Equator and the Polar Circles._
+---------+-------------+----------- _Climates_ |_Longest_| _Latitude._ | _Breadth_ | _Day._ | _D. M._ | _D. M._ ------------+---------+-------------+----------- 1 | 12½ | 8 25 | 8 25 2 | 13 | 16 25 | 8 00 3 | 13½ | 23 50 | 7 25 4 | 14 | 30 25 | 6 30 ------------+---------+-------------+----------- 5 | 14½ | 36 28 | 6 8 6 | 15 | 41 22 | 4 54 7 | 15½ | 45 29 | 4 7 8 | 16 | 49 1 | 3 32 ------------+---------+-------------+----------- 9 | 16½ | 51 58 | 2 57 10 | 17 | 54 27 | 2 29 11 | 17½ | 56 37 | 2 10 12 | 18 | 58 29 | 1 52 ------------+---------+-------------+----------- 13 | 18½ | 59 58 | 1 29 14 | 19 | 61 18 | 1 20 15 | 19½ | 62 25 | 1 7 16 | 20 | 63 22 | 0 57 ------------+---------+-------------+----------- 17 | 20½ | 64 6 | 0 44 18 | 21 | 64 49 | 0 43 19 | 21½ | 65 21 | 0 32 20 | 22 | 65 47 | 0 26 ------------+---------+-------------+----------- 21 | 22½ | 66 6 | 0 19 22 | 23 | 66 20 | 0 14 23 | 23½ | 66 28 | 0 8 24 | 24 | 66 31 | 0 3 ------------+---------+-------------+-----------
CLIMATES _between the Polar Circles and the Poles._
+------------- _Length of Days._ | _Latitude._ -------------------+------------- _Months._ | _D._ _M._ 1 | 67 21 2 | 69 48 3 | 73 37 4 | 78 30 5 | 84 5 6 | 00 00 -------------------+-------------
III. _Of the Poetical rising and setting of the Stars._
[Sidenote: _Cosmical_, _Acronical_, and _Heliacal rising_ and _setting_.]
The ancient Poets make frequent mention of the Stars rising and setting, either _Cosmically_, _Acronically_, or _Heliacally_; whence these distinctions are called _Poetical_.
A Star is said to _rise_ or _set Cosmically_, when it rises or sets at Sun-rising; and when it _rises_ or _sets_ at Sun-setting, it is said to rise or set _Acronically_. A Star _rises Heliacally_, when first it becomes visible, after it had been so near the Sun as to be hid by the splendor of his rays: And a Star is said to _set Heliacally_, when it is first immersed, or hid by the Sun’s rays.
The _Fixed Stars_, and the three superior Planets, _Mars_, _Jupiter_, and _Saturn_, rise _Heliacally_ in the morning; but the Moon rises _Heliacally_ in the evening, because the Sun is swifter than the superior Planets, and slower than the Moon.
IV. _Of the surface of the Earth, considered as it is composed of Land and Water._
The Earth consists naturally of two parts, Land and Water, and therefore it is called the _Terraqueous Globe_. Each of these elements is subdivided into various forms and parts, which accordingly are distinguished by different names.
I. _Of the Land._
The land is distinguished into _Continents_, _Islands_, _Peninsula’s_, _Isthmus’s_, _Promontories_, _Mountains_, or _Coasts_.
[Sidenote: _Continent._]
[Sidenote: _Main Land._]
9. A _Continent_ is a large quantity of land, in which many great countries are joined together, without being separated from each other by the sea: such are _Europe_, _Asia_, _Africa_, and the vast continent of _America_; which four are the principal divisions of the Earth. A continent is sometimes called the _Main Land_.
[Sidenote: _Island._]
10. An _Island_ is a country, or portion of land, environed round with water: such are _Great-Britain_ and _Ireland_; _Sardinia_, _Sicily_, &c. in the _Mediterranean Sea_; the _Isles_ of _Wight_, _Anglesey_, &c. near _England_. Also a small part of dry land, in the midst of a river, is called an island, when compared to a lesser, is called the continent; as if we compare the _Isle_ of _Wight_ to _England_, the latter may be properly called the continent.
[Sidenote: _Peninsula._]
11. A _Peninsula_ is a part of land almost environed with water, save one narrow neck adjoining it to the continent; or which is almost an island: such is _Denmark_ joining to _Germany_; also _Africa_ is properly a large peninsula joining to _Asia_.
[Sidenote: _Isthmus._]
12. An _Isthmus_ is a narrow neck of land joining a peninsula to the continent; as the _Isthmus_ of _Sues_, which joins _Africa_ to _Asia_, that of _Panama_, joining North and South _America_, &c.
[Sidenote: _Promontory._]
[Sidenote: _Mountain._]
13. A _Promontory_ is a high part of land stretching out into the sea, and is often called a _Cape_ or _Headland_: such is the _Cape_ of _Good Hope_ in the South of _Africa_; _Cape Finistre_ on the West of _Spain_; also the _Lizard Point_, and the _Land’s End_, are two Capes or Headlands on the West of _England_. A _Mountain_ is a high part of land in the midst of a country, over topping the adjacent parts.
[Sidenote: _A Coast_ or _Shore_.]
[Sidenote: _Inland._]
14. A _Coast_ or _Shore_ is that part of land which borders upon the sea, whether it be in islands or a continent: And that part of the land which is far distant from the sea, is called the _Inland Country_. These are the usual distinctions of the land.
The Water is distinguished into _Oceans_, _Seas_, _Lakes_, _Gulfs_, _Straits_, and _Rivers_.
[Sidenote: _The Ocean_, or _Main Sea_.]
15. The _Ocean_, or _Main Sea_, is a vast spreading collection of water, not divided or separated by lands running between; such is the _Atlantic_ or _Western Ocean_; between _Europe_ and _America_; the _Pacific Ocean_, or _South Sea_, &c.
_Note_, Those parts of the ocean which border upon the land, are called by various names, according to those of the adjacent countries; as, the _British Sea_, the _Irish Sea_, the _French_ and _Spanish Sea_.
[Sidenote: _A Lake._]
16. A _Lake_ is a collection of deep standing water, inclosed all round with land, and not having any visible and open communication with the sea: But when this lake is very large, it is commonly called a sea; as the _Caspian Sea_ in _Asia_, &c.
[Sidenote: _A Gulf._]
[Sidenote: _Creek_ or _Haven_.]
17. A _Gulf_ is a part of the sea almost encompassed with land, or that which runs up a great way into the land; as, the _Gulf_ of _Venice, &c._ But if it be very large, ’tis rather called an _Inland Sea_; as the _Baltic Sea_, the _Mediterranean Sea_, the _Red Sea_, or the _Arabian Gulf, &c._ And a small part of sea thus environed with land is usually called a _Bay_. If it be but a very small Part, or, as it were, a small arm of the sea, that runs but a few miles between the land, it is called a _Creek_ or _Haven_.
[Sidenote: _A Strait._]
18. A _Strait_ is a narrow passage lying between two shores, whereby two seas are joined together; as, the _Straits_ of _Dover_, between the _British Channel_ and the _German Sea_; the _Straits_ of _Gibralter_, between the _Atlantic_ and the _Mediterranean Sea_. The _Mediterranean_ itself is also sometimes called the _Straits_.
These are all the necessary terms commonly used in _Geography_. The names of the several countries and seas, and all the principal divisions of the Earth, the reader will find expressed upon the Terrestrial Globes. To give a tolerable account of the produce of each country, the genius of the people, their political institutions, _&c._ is properly a particular subject of itself, and quite foreign to our design. We shall next proceed to the use of the Globes; but first it may not be amiss to take a short _review_ of their appurtenances.
Those circles of the sphere that are _fixed_, are (as has been already said) drawn upon the _Globes_ themselves; those that are _moveable_, are supplied by the _Brass Meridian_, the _Wooden Horizon_, and the _Quadrant of Altitude_.
[Sidenote: _Brass Meridian._]
1. That side of the _Brazen Meridian_, which is divided into degrees, represents the _true Meridian_; this side is commonly turned towards the East, and ’tis usual to place the globe so before you, that the North be to the right hand, and the South to the left. The meridian is divided into 4 quadrants, each being 90 degrees, two of which are numbered from that part of the equinoctial, which is above the horizon, towards each of the Poles; the other two quadrants are numbered from the Poles towards the equator. The reason why two quadrants of the meridian are numbered from the equator, and the other two from the Poles, is because the former of these two serve to shew the distance of any point on the globe from the equator, and the other to elevate the globe to the latitude of the place.
[Sidenote: _Wooden Horizon._]
2. The upper side of the wooden frame called the _Wooden Horizon_; represents the true horizon; the circles drawn upon this plane have been already described; we may observe, that the first point of ♈ is the East, and the opposite being the first point of ♎ is the West, the meridian passing through the North and South points.
[Sidenote: _Quadrant of Altitude._]
3. The _Quadrant of Altitude_ is a flexible plate of thin brass, having a nut and screw at one end, to be fastened to the meridian of either globe, as occasion requires. The edge of this quadrant which has the graduations upon it, called the fiducial edge, is that which is always meant whenever we make mention of the quadrant of altitude.
[Sidenote: _Hour Circle._]
4. The _Horary_ or _Hour Circle_, is divided into twice twelve hours, the two XII’s coinciding with the meridian; the uppermost XII is that at _Noon_, and the lowermost towards the horizon is XII at _Night_. The hours on the _East_ side of the meridian are the _Morning Hours_, and those on the _West_ side the _Hours_ after _Noon_. The axis of the globe carries round the _Hand_ or _Index_ which points the hour, and passes through the center of the hour circle.
The things above described are common to both globes; but there are some others which are peculiar or proper to one sort of globe. The two _Colures_, and the _Circles_ of _Latitude_ from the ecliptic, belong only to the _Celestial Globes_; also the ecliptic itself does properly belong only to this globe, tho’ it is always drawn on the Terrestrial, for the sake of those that might not have the other globe by them. The equinoctial on the celestial globe is always numbered into 360 degrees, beginning at the equinoctial point ♈; but on the terrestrial, it is arbitrary, where these numbers commence, according to the meridian of what place you intend for your first; and the degrees may be counted either quite round to 360, or both ways, ’till they meet in the opposite part of the meridian, at 180.
SECT. III.
_The USE of the_ GLOBES.
PROBLEM I. _To find the Latitude and Longitude of any given Place upon the Globe; and on the contrary, the Latitude and Longitude being given, to find the Place._
1. Turn the globe round its axis, ’till the given place lies exactly under the (Eastern side of the brass) meridian, then that degree upon the meridian, which is directly over it, is the _Latitude_; which is accordingly North or South, as it lies in the Northern or Southern hemisphere, the globe remaining in the same position.
That degree upon the equator which is cut by the brazen meridian, is the _Longitude_ required from the first meridian upon the globe. If the longitude is counted both ways from the first meridian upon the globe, then we are to consider, whether the given place lies Easterly or Westerly from the first meridian, and the longitude must be expressed accordingly.
The _Latitudes_ of the following places: and upon a globe where the longitude is reckoned both ways from the meridian of _London_, their longitudes will be found as follow:
_Latitude._ _Longitude._ Deg. Deg. _Rome_ 41¾ North. 13 East. _Paris_ 48¾ N. 2½ E. _Mexico_ 20 N. 102 W. _Cape Horn_ 58 S. 80 W.
2. _The Latitude and Longitude being given to find the Place._
Seek for the given longitude in the equator, and bring that point to the meridian; then count from the equator on the meridian the degree of latitude given, towards the arctic and antarctic Pole, according as the latitude is Northerly or Southerly, and under that degree of latitude lies the _Place_ required.
PROB. II. _To find the Difference of Latitude betwixt any two given Places._
Bring each of the places proposed successively to the meridian, and observe where they intersect it, then the number of degrees upon the meridian, contained between the two intersections, will be the _Difference of Latitude_ required. Or, if the places proposed are on the same side of the equator, having first found their latitudes, subtract the lesser from the greater; but if they are on contrary sides of the equator, add them both together, and the difference in the first case, and the sum in the latter, will be the difference of latitude required.
Thus the difference of latitude betwixt _London_ and _Rome_ will be found to be 9¾ degrees; betwixt _Paris_ and _Cape Bona Esperance_ 83 degrees.
PROB. III. _To find the Difference of Longitude betwixt any two given Places._
Bring each of the given places successively to the meridian, and see where the meridian cuts the equator each time; the number of degrees contained betwixt those two points, if it be less than 180 degrees, otherwise the remainder to 360 degrees, will be the difference of longitude required. Or,
Having brought one of the given places to the meridian, bring the index of the hour circle to 12 o’clock; then having brought the other place to the meridian, the number of hours contained between the place the index was first set at, and the place where it now points, is the difference of longitude in time betwixt the two places.
Thus the difference of longitude betwixt _Rome_ and _Constantinople_ will be found to be 19 degrees, or 1 hour and a quarter; betwixt _Mexico_ and _Pekin_ in _China_, 240 degrees, or 9⅓ hours.
PROB. IV. _Any Place being given to find all those Places that are in the same Latitude with the same Place._
The latitude of any given place being marked upon the meridian, turn the globe round its axis, and all those places that pass under the same mark are in the same latitude with the given place, and have their days and nights of equal lengths. And when any place is brought to the meridian, all the inhabitants that lie under the upper semicircle of it, have their Noon or mid-day at the same point of absolute time exactly.
PROB. V. _The day of the Month being given; to find the Sun’s Place in the Ecliptic, and his Declination._
1. _To find the Sun’s Place_: Look for the day of the month given in the kalendar of months upon the horizon, and right against it you’ll find that sign and degree of the ecliptic which the Sun is in. The Sun’s place being thus found, look for the same in the ecliptic line which is drawn upon the globe, and bring that point to the meridian, then that degree of the meridian, which is directly over the Sun’s place, is the _Declination_ required; which is accordingly either North or South, as the Sun is in the Northern or Southern signs. Thus,
_Sun’s Place._ _Declination._ Deg. Min. Deg. Min. _April 23_ ♉ 3 00 12 32 N. _July 31_ ♌ 7 51 18 20 N. _October 26_ ♏ 2 49 12 28 S. _January 20_ ♒ 0 49 20 07 S.
PROB. VI. _To rectify the Globe for the Latitude, Zenith, and the Sun’s Place._
1. _For the Latitude_: If the place be in the Northern hemisphere, raise the arctic Pole above the horizon; but for the South latitude you must raise the antarctic; then move the meridian up and down in the notches, until the degrees of the latitude counted upon the meridian below the Pole, cuts the horizon, and the globe is adjusted to the latitude.
2. _To rectify the Globe for the Zenith_: Having elevated the globe according to the latitude, count the degrees thereof upon the meridian from the equator, towards the elevated Pole, and that point will be the zenith or the vertex of the place; to this point of the meridian fasten the quadrant of altitude, so that the graduated edge thereof may be joined to the said point.
3. Bring the Sun’s place in the ecliptic to the meridian, and then set the hour index to XII at Noon, and the globe will be rectified _to the Sun’s Place_. If you have a little mariner’s compass, the meridian of the globe may be easily set to the meridian of the place.
PROB. VII. _To find the Distance between any two given places upon the Globe, and to find all those places upon the globe that are at the same distance from a given place._
Lay the quadrant of altitude over both the places, and the number of degrees intercepted between them being reduced into miles, will be the distance required: Or, you may take the distance betwixt the two places with a pair of compasses, and applying that extent to the equator, you’ll have the degrees of distance as before.
_Note_, A _geographical mile_ is the ¹/₆₀th part of a degree; whereof if you multiply the number of degrees by 60, the product will be the number of geographical miles of distance sought; but to reduce the same into _English_ miles, you must multiply by 70, because about 70 _English_ miles make a degree of a great circle upon the superficies of the Earth.
Thus, the distance betwixt _London_ and _Rome_ will be found to be about 13 degrees, which is 780 geographical miles.
If you rectify the globe for the latitude and zenith of any given place, and bring the said place to the meridian; then turning the quadrant of altitude about, all those places that are cut by the same point of it, are at the same distance from the given place.
PROB. VIII. _To find the angle of position of Places, or the angle formed by the meridian of one Place, and a great circle passing through both the Places._
Having rectified the globe for the latitude and zenith of one of the given places, bring the said place to the meridian, then turn the quadrant of altitude about, until the fiducial edge thereof cuts the other place, and the number of degrees upon the horizon, contained between the said edge and the meridian, will be the angle of position sought.
Thus, the angle of position at the _Lizard_, between the meridian of the _Lizard_ and the great circle, passing from thence to _Barbadoes_ is 69 degrees South-Westerly; but the angle of position between the same places at _Barbadoes_, is but 38 degrees North-Easterly.
_SCHOLIUM_
The angle of position between two places is a different thing from what is meant by the bearings of places; the _Bearings_ of two places is determined by a sort of spiral line, called a _Rhumb Line_, passing between them in such a manner, as to make the same or equal angles with all the meridians through which it passeth; but the _angle_ or _position_ is the very same thing with what we call the azimuth in astronomy, both being formed by the meridian and a great circle passing thro’ the zenith of a given place in the heavens, then called the azimuth, or upon the Earth, then called the angle of position.
From hence may be shewed the error of that geographical paradox, _viz._ If a place A bears from another B due West, B shall not bear from A due East. I find this paradox vindicated by an author, who at the same time gives a true definition of a rhumb line: But his arguments are ungeometrical; for if it be admitted that the East and West lines make the same angles with all the meridians through which they pass, it will follow that these lines are the parallels of latitude: For any parallel of latitude is the continuation of the surface of a _Cone_, whose sides are the radii of the sphere, and circumference of its base the said parallel; and it is evident, that all the meridians cut the said surface at right (and therefore at equal) angles; whence it follows, that the rhumbs of East and West are the parallels of latitude, though the case may seem different, when we draw inclining lines (like meridians) upon paper, without carrying our ideas any farther.
PROB. IX. _To find the_ Antœci, Periœci, _and_ Antipodes _to any given place._
Bring the given place to the meridian; and having found its latitude, count the same number of degrees on the meridian from the equator towards the contrary Pole, and that will give the place of the _Antœci_. The globe being still in the same position, set the hour index to XII at noon, then turn the globe about ’till the index points to the lower XII; the place which then lies under the meridian, having the same latitude with the given place, is the _Periœci_ required. As the globe now stands, the _Antipodes_ of the given place are under the same point of the meridian, that its _Antœci_ stood before: Or, if you reckon 180 degrees upon the meridian from the given place, that point will be the _Antipodes_. Let the given place be _London_, in the latitude of 51½ degrees North, that place which lies under the same meridian and the latitude 51½ degrees South, is the _Antœci_; that which lies in the same parallel with _London_, and 180 degrees of longitude from it, is the _Periœci_, and the _Antipodes_ is the place whose longitude from _London_ is 180 degrees, and latitude 51½ degrees South.
PROB. X. _The Hour of the Day at one place being given; to find the correspondent Hour (or what o’Clock it is at that time) in any other place._
The difference of time betwixt two places is the same with their difference of longitude; wherefore having found their difference of longitude, reduced into time (by allowing one hour for every 15 degrees, _&c._) and if the place where the hour is required lies (Easterly/Westerly) from the place where the hour is given, (add/subtract) the difference of longitude reduced into time (to/from) the hour given; and the sum or remainder will accordingly be the hour required. Or,
Having brought the place at which the hour is given to the meridian, set the hour index to the given hour; then turn the globe about until the place where the hour is required comes to the meridian, and the index will point out the hour at the said place.