Imágenes de páginas
[merged small][graphic][ocr errors]

1. Terrestrial Globes. Though the earth be not exactly every 5th or 10th degree of latitude and longitude, accorda sphere, it deviates very little from the spherical form. ing to the size of the globe. These lines point out accu. The polar diameter is less than the equatorial by about rately the latitude or longitude of those places which are 1334th of the latter, while the height of the highest moun. situated upon them, and give us a general idea of the situtain is not equal to the 2000th part of it. Upon the lar- ation of oiher places. gest globe that is ever constructed, these differences of the Besides meridians and parallels of latitude, the ccliptic earth from an exact sphere could not be perceived; and is usually drawn upon globes, and also the tropics and the artificial globe, therefore, is always exactly spherical. polar circles. All these last are commonly drawn with

Through the centre of the globe let a straight wire pass, double lines to distinguish them from other meridians and this will represent the axis, and the points where it cuts parallels of latitude. the surface, the north and south poles. A circle drawn at The globe suspended in the general meridian, is placed the distance of 90 degrees from either pole is the equator, upon a wooden frame. The upper surface of this frame and another circle drawn from any point of the equator, divides the globe into two hemispheres, one superior, and and at right angles to it, will be the first meridian. the other inferior, and represents, therefore, the rational

The equator and the first meridian are divided into de- horizon of any place which is brought to the zenith point grees and minutes, which are numbered, beginning at the of the meridian. There are two notches for the meridian point where the circles intersect each other. The degrees to slide in, by which different elevations of the pole may upon the first meridian are numbered on both sides of the be exhibited. The horizon has commonly drawn upon it equator, and do not exceed 90. They point out the lati- the points of the compass, the twelve signs of the zodiac, tude. The degrees upon the equator are numbered com- the months of the year, &c. pletely round the circle, and extend therefore to 360. They There is attached to the general meridian a quadrant, enable us to find out the longitude.

composed of a thin pliable plate of brass, answering exactThe equator and first meridian are distinguished from ly to a quadrant of the meridian. It is graduated, and has parallels of latitude and other meridian lines, by their a notch, nut, and screw, by which it may be fixed to the being graduated. They are also sometimes denoted by brazen meridian in the zenith of any place. When so fixdouble lines.

ed, it turns round a pivot, and supplies the place of vertiWe shall now suppose, that the artificial globe exactly cal circles. It is hence denominated a quadrant of altirepresents the surface of the earth, and proceed to explain tude. the lines which are commonly drawn upon the globe, be- A small circle of brass is placed on the north pole. It sides the equator and first meridian, and to describe the is divided into 24 equal parts, and is termed an hour-circle. apparatus usually attached to it.

On the pole of the globe is fixed an index, which turns In order that we might be able to find out from the globe round the axis, and points out the hours upon the hour. itself, the latitude and longitude of any place, a parallel to circle. the equator and a meridian line would require to be drawn There is also often attached to the globe a compass, through that place. It is impossible that such lines could which is placed upon the pediment of the framie, parallel be drawn through every point on the globe, and it is un- to the horizon. necessary, for the brass circle placed around it, enables us 2. Problems solved by the Globe. Having thus described to find out the latitude and longitude. In this circle, the globe and its apparatus, we shall now explain some of which is placed at right angles to the equator, and is there the problems that may be resolved by it. fore a meridian, the globe is suspended by the axis. One 1.' To find the latitude and longitude of any place. We of the sides of the meridian is graduated, or divided into have already seen, that this is done by bringing the place degrees, minutes, and seconds. The globe can be turned to the graduated side of the general meridian; the degree round its axis, while the general meridian remains station of the meridian cut by the place being equal to the latiary, so that every point of the surface of the globe must tude, and the degree of the equator then under the meripass under some point of the meridian. To find out the dian being the longitude. latitude and longitude of any place, therefore, we have II. To find a place upon the Globe, its latitude and lon. only to turn the globe round till the given place be brought gitude being given. Find the degree of longitude on the to the meridian. The number of degrees, minutes, &c. equator, and bring it to the brass meridian ; then find the under which the place lies will be its latitude, and the degree of latitude on the meridian, either north or south, number intercepted upon the equator its longitude. and the point of the globe under that degree of latitude is

In addition to the general meridian, meridians and paral- the place required. les of latitude are usually drawn upon the globe, through III. To find all the places on the Globe that have the same latitude as a giren place, suppose New York. — Turn the place that comes under the same point of the meridian globe round, and all the places that pass under the same where New York was, is where the periæci dwell, or peopoint of the meridian as the given place does, have the ple that have the same seasons, and at the same time, as same latitude with it.

New York, and the same length of the days and nights, IV. To find all the places that hare the same longitude but have an opposite hour, it being midnight with the one or hour with a giren place, as New York. — Bring the give when noon with the other. Lastly, While the place of the en place, New York, to the meridian, and all places then periæci is at the meridian, count by the meridian the same under the meridian have the same longitude.

degree of latitude south, and that will give the place of the V. To find the difference in the time of the day at any two antipodes of New York. They have all their hours and giren places, and their difference of longitude. - Bring one seasons opposite to those of New York, being noon with of the places to the meridian, and set the hour-index to the one when midnight with the other, and winter with twelve at noon, then turn the globe till the other place the one when summer with the other. come to the meridian, and the index will point out the dif- IX. To find the sun's place in the ecliptic and also on the ference of time. By allowing 15 degrees to every hour, Globe at any giren time. — Find in the calendar, on the or one degree to four minutes of time, the difference of wooden horizon, the given month, and day of the month, longitude will be known. The difference of longitude and immediately opposite will be found the sign and de. may also be found without the time, in the following man. gree which the sun is in on that day. Then in the eclipner :- Bring each of the places to the meridian, and tic drawn upon the globe, find the same sign and degree, mark the respective longitudes. Subtract the one num. and that will be the place of the sun required. ber from the other, and we obtain the difference of longi- X. The time being giren at any place, to find the place tude sought.

on the earth to which the sun is then rertical. Find the VI. The time being knoucn at any giren place, as New sun's place on the globe by the last problem; and turn the York, to find that hour it is in any other part of the world. globe about till that place come to the meridian; mark - Bring ihe given place, to the meridian, and set the index the degree of the meridian over it, which will show the to the given hour; then turn the globe till the other place latitude of the required place. Then turn the globe ull the come to the meridian, and the hour at which the index given place come to the meridian, and set the index of points will be the time sought.

the hour-circle to the given moment of time. Lastly, Turn VII. To find the distance of two places on the Globe. the globe till the index points to twelve at noon, and the If the two places be either both on the equator or both on place of the earth corresponding to that upon the globe, the same meridian, the number of degrees is the distance which stands under the meridian at the point marked as between them, reduced into miles, at the rate of 69f to the before, is that which has the sun at the given time in the degree, will give the distance nearly. If the places be in zenith. any other situation, lay the quadrant of allitude over them, XI. To find all those places on the earth to which the sun and the degrees intercepted upon it by the two places, and is vertical on a giren day. - Find the sun's place in the turned into miles, as above, will give their distance. ecliptic on the globe, as in the last problem, and bring that

VIII. To find the antæci, periæci, and antipodes * of any place to the meridian. Turn the globe round, and note all giren place, suppose Vero York. — Bring New York to the the places which pass under the same point. These will Teridian, and find by the meridian the point upon the be the places sought. This problem enables us to deterpo! !). of which the latitude is as much south as that of mine what people are ascii on any given day. It is evi. New York is north. The place thus arrived at will be the dent, that in a similar manner we may also find to what situation of the anteci, where the hour of the day or night places on the earth the moon or any other planet is vertical is always the same as at New York, and where the seasons at a given time: the place of the planet on the globe at and lengths of the days and nights are also the same, but that time being found by its declination and right ascension. at opposite times of the year. New York being still under XII. A place being given in the torrid zone, to find on the meridian, set the hour-index to 12 at noon, or pointing what two days of the yeur the sun is vertical at that place.towards New York, then turn the globe half round, till the Bring the given place to the meridian, and note the degree index points to the opposite hour, or 12 at night. The it passes under. Turn the globe round, and note the iwo

points of the ecliptic which pass under the same degree of * Asrii, Amphiscii, Heteroscu, and Periscii. The inhabi- ihe meridian. Then, find by the wooden horizon on what tants of the different regions of the earth are sometimes dis- days the sun is in these two points of the ecliptic, and on tinguished by the ancient geographers, according to the direc- these days he will be vertical to the given place. tion of their shadows. When the sun at mid-day is vertical XIII. To find how long the sun shines without setting in to any place, the inhabitants of that place were said to be ascii, that is, without shadow. All the inhabitants between grees of latitude of the given place from 90, which gives

any giren place in the frigid zone. — Subtract the dethe tropics must be ascii iwice a year. The inhabitants of the torrid zone, having the sun some

the complement of the latitude, and count this completimes to the north, and sometimes to the south, will project ment upon the meridian from the equator towards the shadows directed by turns towards cither pole, and they were

pole, marking that point of the meridian; then turn the therefore said to be amphiscii, that is, having both kinds of globe round, and observe what two degrees of the ecliptic shadows.

pass exactly under the point marked on the meridian.' It Those who inhabit the temperate zones were called hetero- is evident, that the sun will shine upon the given place scii, because their shadows fall in opposite directions. without setting while it is in these, and all the points of

Within the polar circles the inliabitants must, for a while, the ecliptic that are nearer to the given place. Find, project shadows in all directions, and they are therefore said therefore, upon the wooden horizon the months, and days to be periscii. Periæci and Antæci, and Antipodes. The seasons which

of the months in which the sun is in the two points in the inhabitants of opposite places on the earth enjoy at the

question, and the intermediate time will be that during same time, as well as the hours of the day at these places, be

which the sun constantly shines at the given place. ing contrasted, give rise to certain distinctions with which it

XIV. To find how long the sun nerer shines upon any is also necessary to be acquainted.

giren place in the frigid zones. — Count the complement of Those who live under opposite meridians, at equal distan. latitude towards the south, or farthest pole, and then proces from the equator, and upon the same side of it, are term- ceed exactly as in the last problem. cd peripei. They have the same seasons, but reckon at the XV. To rectify the globe to the latitude of any place. some instant opposite hours : it being midnight with the one Move the brass meridian in its groove, till the elevation of when mid-day with the other.

the pole above the horizon be equal to the latitude. Those who live under the same meridian on opposite sides of the equator, and at equal distances from it, are called an.

XVI. To rectify the globe to the horizon of any place. tuci. They have the seasons at opposite times, but reckon at Rectify the globe to the latitude of the place by the last the same instant the same hours.

problem; and then turn the globe on its axis till the given The people who live at equal distances from the equator, place come to the meridian. The place will then be ex. and under opposite meridians, are termed antichthones, or an- actly on the vertex of the globe, 90 degrees distant every tipodes. They have both the seasons and the hours of the way from the wooden horizon ; and that horizon, theres day at opposite times.

fore, will represent the horizon of the given place.

XVII. To find the bearing of one place from another, whole of the eclipse will be visible. A part of it at the and their angle of position. — Rectify the globe to the ho- end will be seen in places which are near to the lower side rizon of one of the places. Screw the quadrant of alti- of the western part of the horizon. If the eclipse be lunar, tude to the zenith point of the meridian, and make it the moon will be in the opposite point of the ecliptic to revolve till the graduated edge passes through the other the sun, and vertical to that point of the earth which is place. Then look on the wooden horizon for the point of opposite to the place to which the sun is vertical. The the compass, or number of degrees from the south, where eclipse, therefore, will be visible in the lower hemisphere. the quadrant of altitude meets the horizon, and that will be XX. To find the beginning and end of twilight, on any the bearing of the latter place from the former, or the an- day of the year, for any latitude. — It is twilight in thi gle of position sought.

evening from sunset till the sun is 18 degrees below XVIII. To find all those places on the earth to which the horizon; and in the morning from the time the si the sun at a given time is rising or setting ; also what pla, is within 18 degrees of the horizon till the moment of ces are then illuminated by the sun, or in darkness; and his rising. Therefore, rectify the globe to the given lati where it is noon, or midnight. — Find the place to which lude, set the index of the hour-circle to 12 at noon, and the sun is vertical at the given time, and rectify the globe screw on the quadrant of altitude. Find the point ol to its horizon, in which state the place will be in the ze- the ecliptic which is opposite to the sun's place, ang nith point of the globe. Then is all the hemisphere above turn the globe on its axis westward along with the quadran the wooden horizon enlightened, or in daylight, while the of altitude, till that point cut the quadrant in the 18th hemisphere below the horizon is in darkness, or night; degree below the western side of the horizon. The in lastly, to all these places by the eastern side of the hori- dex will then show the time of dawning in the morning zon, the sun is just setting, and to those by the western Next turn the globe and quadrant of altitude towards the side, he is just rising.

east, till the same opposite point of the ecliptic meet the XIX. The time of a solar or lunar eclipse being given, quadrant the 18th degree below the eastern side of the hoto find all those places at which the eclipse will be visible. – rizon. The index will then show the time when twilight Find the place to which the sun is vertical at the given ends in the evening. time, and rectify the globe to the horizon of that place. XXI. To rectify the globe to the present situation of the Then, by the last problem, it is evident, that if the eclipse earth. — Rectify the globe to the horizon of the place. Its be solar, a part of it at the beginning only will be seen in situation will then correspond to that of the earth; and, places which are not far above the eastern side of the ho- if it stand in the sun, it will be illuminated as the earth rizon ; while, in the rest of the upper hemisphere, the is.

[merged small][merged small][merged small][ocr errors][merged small][merged small][merged small]



1. Northern and Southern Hemispheres. The terraqueous globe is divided by the equator into two equal parts, called the Northern and Southern Hemispheres. But the slightest glance at a map of the world will show, that there is a much greater accumulation of dry land in the former than in the latter ; recent voyages have, indeed, shown, that this inequality is not so great as was thought by geographers of the last century, large masses of land having been discovered in the Antarctic Seas, and the northern coasts of Asia and America having been shown not to extend so far north as was once supposed. The following statement will show the comparative distribution of land and water in the two hemispheres. If we divide the whole surface of the earth into 1000 parts, we shall find


In the whole sphere,

266 parts.

734 parts.
Southern Hemisphere,
Northern Hemisphere,

197.2 66

302.8 66

68.7 66






Himmalah Mo


[ocr errors]






[ocr errors]

The whole of Asia, Europe, and North America, much the greater part of Africa, and a part of South America, lie north of the equator, and large masses of land advance to within 25 degrees of the north pole, and considerable tracts much nearer. While only a small portion of Africa, with New Holland, the bulk of South America, and some islands, rise above the

waters in the south.

There is, indeed, a much North

larger tract about the Arctic Ocean

south than around the British

north pole, that has not Siber ia

been explored, and it is Paris EUROPE Altai Mus

now ascertained that an Alps

Antarctic continent lies Algiers


in that quarter. Amer



ica reaches only to 56° China

South Lat., Africa to
Great Desert


34°, and New Holland


to 45°, while on the Guinea Guardafia

north, Asia, Europe, Mis of the Moon


and America, project AFRICA



above the 70th parallel Congo


of latitude. Madagascar

2. Eastern and West. St Helena Hotten,

ern Hemisphere. The OCEAN

two great continents of ColGood Hope

Pt Jackson

which the land is com

posed, are commonly so Van Diemens Land

projected on maps as to form two separate hemi

spheres. The eastern SOUTHERN OCEAN

then includes, in addi

tion to the continental South

portion, New Holland

and the islands around Eastern Hemisphere.

it; and the western com




[ocr errors]




[ocr errors][merged small][merged small]


The distribution prises most of the small islands of the Pacific with the American continent. of land and water is not less unequal in this than in the former division. Thus we have


In the Eastern Hemisphere,

320 parts.
In the Western Hemisphere, 414


186 parts.

[ocr errors]





[ocr errors]





[ocr errors]


Sandwich Is


C.Verd is
I ndios

Another striking circumstance in the conformation of the two continents, is the different disposition of the land in each. In the old continent, the principal extension is to the west and east, the breadth from north to south being comparatively inconsiderable, particularly if we leave out the southern tongue of Africa ; in the new, the great extension is from north to south.

In the former, we may draw continuous straight lines over land of great extent, but in the latter, in order to draw lines of much length, it will be necessary to make them winding. Thus a straight line from the Gulf of Guinea to the northwestern coast of Siberia is 9,000 miles in length; the longest straight line we can draw on the new continent is from Cumana to Terra del Fuego, 5,400 miles. Conformable to this general extension of the land, is the Northern Coast.

direction of the great

mountain chains in the North

two hemispheres. The Arctic Sea

Rocky Mountains, the

Cordilleras, and the AnDavis st

des, stretch north and south ; while starting

with the Pyrenees and NAMERICA

the Alps in Europe, we JUNITED STATES Boston

may follow an almost unWashington Norleans

broken chain of lofty

mountains, comprising the Hawaii

Tauro-Caucasian, HimaPACIFIC OCEAN

Orinoco R

laya, and other Asiatic Quito

chains, to the shores of Galapagos ISSAMERICA

the Pacific ocean. Even Society I Lima Brazil

the direction of the small

er portions of both conFriendly Otaheite

tinents, as their islands - and peninsulas, nearly coincides with the general

course of the great mounFuega

tain chains.

We shall now proceed to describe the different countries and states of

the globe under the folSouth

lowing heads and in the Western Hemisphere.

following order; 1. North America. — 2. West Indies. — 3. South America. - 4. Europe. - 5. Africa.

. - — — - 6. Asia. —7. Oceanica.

Giving first a general description of each division, sketching its physical and political features, and pointing out its minerals, plants, animals, and inhabitants, we shall then pass to a more particular consideration of the separate parts of which it consists.

Imazon R


Cast Roque


[blocks in formation]
« AnteriorContinuar »