Page images

the ecliptic never lets in the former case, and as much of the opposite

part never rises in the latter

. And the nearer unto, or the more remote from the pale thefe places are, the longer or shorter is the sun's continuing pre

13. If a thip fets out from any port, and fails round the earth eaftward to the same port again, let her perform her voyage in what time the will, the people in that fhip, in reckoning their time, will gain one cornplete day at their return, or count one day more than those who refide at the fame port; because, by going contrary to the fun's diurnal motion

, and being forwarder every evening than they were in the morning, their horizon will get so much the sooner above the setting fun, than if they had kept for a whole day at any particular place. And thus, by cutting off from the length of every day a part proportionable to their own motion, they will gain a coinplete day at their return, without gaining one moment of absolute time. If they sail westward, they will reckun one day lets than the people do who retide at the same port'; because, by gradually following the apparent diurnal motion of the sun, they will keep him each particular day so much longer above the horizon as answers to that day's course; and thereby cut off a whole day in reckoning, at their return, without losing one moment of absolute time.

Hence, if two ships should set out at the same time from any port, and fail round the globe, one eastward and the other westward, so as to meet at the same port on any day whatever, they will differ two days in reckoning their time, at their return. If they fail twice round the earth, they will differ four days; if thrice, then fix, &c.

OF THE NATURAL DIVISIONS OF THE EARTH. THE constituent parts of the earth are two, the land and water. The parts of the land are continents, iflands, peninsulas, isthmuses, promontories, capes, coasts, mountains, &c. This land is divided into two great continents (besides the illands), viz. the eastern and western continent. The eastern is fubdivided into three parts, viz. Europe, on the northweft; Asia, on the north-east; and Africa (which is joined to Afia by the fthmus of Suez, 60 miles over), on the fonth. The western continent tonfifts of North and South America, joined by the ifthmus of Darien, learly 70 miles broad.

A continent is a large portion of land, containing several countries or lingdoms, withont any entire feparation of its parts by water, as Europe. d is a smaller part of land, quite surrounded by water, as Great infula is a tract of land, every where surrounded by waDeck, by which it joins the neighbouring The parts of the water are oceans, seas, lakes, ftraits, gulfs, bays or creeks, rivers, &c. The waters are divided into three extensive oceans (besides lefser seas, which are only branches of these), viz. the Atlantis, the Pacific, and the Indian Ocean. The Atlantic, or Western Ocean, divides the eastern and western continents, and is 3000 miles wide.

and that neck of land which lo of Suez, which joins Africa

and South Ame

to the

The Pacific divides America from Afia, and is 10,000 miles over. The Indian Ocean lies between the Eat Indies and Africa, being 3000 miles wide.

An ocean is a vast collection of water, without any entire separation of its parts by land; as the Atlantic Ocean. A sea is a smaller collection of water, which communicates with the ocean, confined by the land; as the Mediterranean and the Red Sea. A lake is a large collection of water, entirely furrounded by land; as the lake of Geneva, and the lakes in Canada. A frait is a narrow part of the sea, confined or lying between two fhores, and opening a passage out of one sea into another; as the strait of Gibraltar, or that of Magellan. This is sometimes called a found; as the strait into the Baltic. A gulf is a part of the sea running up into the land, and surrounded by it, except at the passage whereby it communicates with the sea or ocean. If a gulf be very large, it is called an inland sea, as the Mediterranean ; if it do not go far into the land, it is called a bay, as the Bay of Biscay; if it be very small, a creek, haven, Nation, or road for ships, as Milford Haven. Rivers, canals, brooks, &c. need no description ; for these lesser divisions of water, like those of land, are to be met with in most countries, and every one has a clear idea of what is meant by them. But in order to strengthen the re membrance of the great parts of the land and water we have described, it may be proper to observe that there is a strong analogy or resemblance between them. The description of a continent resembles that of an ocean; an ifland encompassed with water resembles a lake encompassed with land. A peninsula of land is like a gulf or inland sea. A promontory or cape of land is like a bay or creck of the sea; and an isthmus, whereby two land: are joined, resembles a strait, which unites one sea to another.

To this description of the divisions of the earth, we shall subjoin a table exhibiting the superficial contents of the whole globe in square miles, fixty to a degree, and also of the feas and unknown parts, the habitable earth the four.quarters or continents ; likewise of the great empires and prin cipal itlands, placed as they are subordinate to each other in magnitude.

[ocr errors]



Square Inlands.



Miles. The Globe 149,510,627 Cuba

38,400 St. Michael

9201 Seas and unknown Parts .. 117,843,321 Java

38,250 Sky

9001 The Habitable World • 30,666,806 Hispaniola 36,000 Lewis

S80 Europe 2,749,349 Newfoundland 35,500 ugen

768) AGA 10,257,487 Ceylon...... 27,730 Yvica

625 Africa 8,506,208 Ireland.. 27,457 Minorca

520 America.. 9,153,762 Formosa 17,000 Rhodes.

2808 Perfian Empire ander Darius 1,650,000 Anian 11,900 Cephalonia 420 Rom. Em. in its utmost height 1,610,000 Gilolo... 10,400 Amboyna ... 400 Ruffian

3,576,485 Sicily

9,400|Orkn. Pomona 3241 Chinese 1,749,000 Timor ...... 7,800 Scio

3001 Great Mogul.

1,116,000 Sardinia 6,600 Martinico 260 Turkish 960,057 Cyprus.. 6,300 Lemnos..

220 British, exclusive of Setike- ? Jamaica 6,000 Corfu

194 809,996 ments in Africa and Gibraltar


.6,000 Providence 169 Present Perlian ....

800,000 Ceram
5,400 Man.

4,000 Bornholm

1601 ISLANDS. Socotra, 3,600 Wight

1501 Bomeo 228,000 Candia.. 3,220 Malta

150 Madagascar.

168,000 Porto Rico 3,200 Barbadoes. 140 Sumatra 129,000 Corsica ... 2,520 Zante

120 Japan 118,000 Zealand 1,935 Antigua

1001 Great Britain

72,920 Majorca 1,400 St. Christopher's 80 Celebes 69,400 St. Jago 1,400 St. Helena..

80 Manilla 58,500 Negropont 1,300 Guernsey

50 Iceland 46,000 Teneriffe.... 1,272 Jersey

43 Terra del Fuego

42,075 Gothland.... 1,000 Bermudas Mindanao

39,200 Madeira

950 Rhode



To these inands may be added the following, which have lately been discovered Jor more fully explored. The exact dimensions of them are not ascertained: but they may be arranged in the following order, according to their magnitude, beginning at the largeft, which is supposed to be nearly equal in fize to the whole continent of Europe : New Holland,

Oraheite, or King George's Illand,
New Guinea,

Friendly Iands,
New Zealand,

New Caledonia,

Eafter or Davis's INand.
New Hebrides,


153 Millions

• The number of inbabitants com

Europe contains.. puted at present to be in the known world, at a medium, taken from the best calculations, are about 953 millions.

Total 953 WINDS AND Tides.] We cannot finish the doctrine of the earth, without considering the winds and tides, from which the changes that happen on its surface principally arise.

Winds.] The earth on which we live is every where furrounded by a fine invifble fluid, which extends to several miles above its surface, and is called Air. It is found by experiments, that a small quantity of air is capable of being expanded, so as to fill a very large space, or to be compressed into a much smaller compass than it occupied before. The gem neral cause of the expansion of the air is heat; the general cause of its compreffion is cold. Hence if any part of the air or atmosphere receive a greater degree of cold or heat than it had before, its parts will be put in motion, and expanded or compressed. But when air is put in motion we call it wind in general, and a breeze, gale, or storm, according to the quickness or velocity of that motion. Winds, therefore, which are commonly confidered as things extremely variable and uncertain, depend a general cause, and act with more or less uniformity in proportion as the action of this cause is more or less constant. It is found by observation, made at fea, that, from thirty degrees north latitude, to thirty degrees fouth, there is a constant eaft wind throughout the year, blowing on the Atlantic and Pacific oceans, and called the Trade Il’ind. This is occa fioned by the action of the sun, which, in moving from east to west, heats, and consequently expands the air immediately under him ; by which means. a stream or tide of air always accompanies him in his course, and occasions a perpetual east wind within these limits. This general cause however is, modified by a number of particulars, the explication of which would be too tedious and complicated for our present plan, which is to mention facts rather than theories,


The winds called the Tropical IV'inds, which blow from some parti, cular point of the compass without much variation, are of three kinds ; 1. The General Trade Winds, which extend to nearly thirty degrees of latitude on each side of the equator in the Atlantic, Ethiopic, and Pacific seas. 2. The Monsoons, or shifting trade winds, which blow fix months in one direction, and the other six months in the opposite. These are mostly in the Indian or Eastern Ocean, and do not extend above two hundred leagues from the land. Their change is at the vernal and autumnal equinoxes, and is accompanied with terrible storms of thunder, lightning and rain. 3. The Sea and Land Breezes, which are another kind of periodical winds, that blow from the land from midnight to midday, and from the fea from about noon till midnight; these, however, do not extend above two or three leagues from shore. Near the coaft of Guinea in Africa, the wind blows nearly always from the west, south-welt, or fouth. On the coast of Peru in South America, the wind blows conftantly from the south-west. Beyond the latitude of thirty north and south, the winds, as we daily perceive in Great Britain, are more variable, though they blow oftener from the west than any other point. Between the fourth and tenth degrees of north latitude, and between the longitude of Cape Verd and that of the easternmost of the Cape Verd islands, there is a tract of fea condemned to perpetual calms, attended with terrible thunder and lightning, and such rains, that this sea has acquired the name of the Rains.

It may be also useful to students in navigation and geography to observe farther, that the course or latitude our ships generally keep in their patrage from England to America, and the West Indies, is,

To Bolton in New England, and Halifax in Nova Scotia, from 12 to 43 degrees.

To New York by the Azores, or Western Ilands, 39 degrees.

To Carolina and Virginia by Madeira, which is called the upper course, 32 degrees; but the usual course, to take advantage of the trade-winds, is from 16 to 23 degrees; and in this course they frequently touch at Antigua : it is this course our West India fips sail in.

The Spanit galleons and the Aota from Spain keep from 15 to 18 degrees; and in their reurn to Spain, about 37 degrees.

Tides.] By the tiles is meant that regular motion of the sea, according to which it ebbs and flows twice in twenty-four hours. The doctrine of the tides remained in obscurity, till the immortal fir Isaac Newton explained it by his great principle of gravity or attraction. For, having demonstrated that there is a principle in all bodies within the folar system, by which they mutually draw or attract one another in proportion to their distance, it follows, that those parts of the sea which are immediately below the moon, must be drawn towards it; and consequently, wherever the moon is nearly vertical, the sea will be raised, which oc. casions the flowing of the tide there. A similar reason occasions the flowing of the tide likewise in those places where the moon is in the nadir, and which must be diametrically opposite to the former : for in the hemisphere farthest from the moon, the parts in the nadir being less attracted by her than the other parts which are nearer to her, gravitate less towards the earth's centre, and consequently must be higher than the rest. Those parts of the earth, on the contrary, where the moon appears on the horizon, or ninety degrees distant from the zenith and nadir, will have low water; for as the waters in the zenith and nadir rise at the same time, the waters in their neighbourhood will press towards those places to maintain the equilibrium ; to supply the places of these, others will move the same way, and so on to the places ninety degrees distant from the zenith and nadir, where the water will be lowest

. By combining this doctrine with the diurnal motion of the earth, above explained, we shall be sensible of the reason why the tides ebb and flow twice in a lunar day, or about twentyfour hours fifty minutes.

The tides are higher than ordinary, twice every month, that is about the times of new and full moon, and are called Spring-Tides : for at these times the actions of both the sun and moon are united, and draw in the same ftraight line; and consequently the sea must be more elevated. At the conjunction, or when the sun and moon are on the same side of the earth, they both conspire to raise the waters in the zenith, and confequently in the nadir; and at the opposition, or when the earth is between the sun and moon, while one occasions high water in the zenith and nadir, the other does the fame. The tides are less than ordinary twice every month, about the first and last quarters of the moon, and are called Neap-Tides : for in those quarters, the sun raises the waters where the moon depresses them, and depresses where the moon raises them ; so that the tides are only occasioned by the difference by which the action of the moon, which is nearest us, prevails over that of the fun. These things would happen uniformly, were the whole surface of the earth covered with water ; but since there are a multitude of islands and continents which interrupt the natural course of the water, a variety of appearances are to be met with in different places, which cannot be explained without considering the situation of the shores, straits, and other objects that have a share in producing them.

CURRENTS.] There are frequently streams or currents in the ocean, which set fhips a great way beyond their intended course. There is a current between Florida and the Bahama Inlands, which always runs from fouth to north. A current runs conftantly from the Atlantic, through the straits of Gibraltar, into the Mediterranean. A current sets out of the Baltic sea, through the sound or strait between Sweden and Denmark, into the British channel, so that there are no tides in the Baltic. Abont small islands and head-lands in the middle of the ocean, the tides rise very little ; but in some bays, and about the mouths of rivers, they rise from 12 to 30 feet.

Maps.] A map is the representation of the earth, or a part of it, on a plane furface. Maps differ from the globe in the same manner as a picture does from a statue. The globe truly represents the earth; whereas a map, being a plane surface, cannot represent a spherical body. But though the earth can never be exhibited exactly by one map, yet by

« PreviousContinue »