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the sea-eagle, or osprey, is more common. The temperate zone is remarkable for the migration of birds as well as fishes; the stork and the crane, as well as the swallow, instinctively selecting their summer as well as winter abodes, and the same individual birds sometimes return. ing in spring to the same nests they left in autumn. The parrot tribes seem confined to the East Indies, the south-east of Asia, and the shores of Western Africa; while the celebrated birds of Paradise are found in New Guinea and its neighbourhood alone. M. Humboldt has asserted, and is confirmed in it by the distinguished naturalist Latrielle, that no quadruped, terrestrial bird, and hardly any insect is common to the New and Old worlds. We must beg leave, however, to doubt the correctness of this last item. See our article ENTomology. There are, at any rate, certain useful animals which thrive almost equally in all the zones, till the severity of the polar frosts chills them, or the hardened ground refuses subsistence. “In this class, beneficent nature has placed all those whose services, in a domesticated state, are most useful to man; the horse, the ox, the sheep, the hog, the goat, the dog, and the cat. Others may be added, in the wide diffusion of which nature cannot be considered as having been so bounteous; among these are the fox, the hare, the rabbit, the stag, the rat, and the mouse. These common features, however, leave room for others, in which the different climates are widely distinguished from each other.’ “In the torrid zone, it has been justly observed, we find the same rank luxuriance of animal as of vegetable life. The inundated meadows, and the banks of rivers, are covered with the most overgrown and gigantic forms. The mighty elephant here dwells in the depths of the ancient forests, while the rhinoceros, and the hippopotamus, roll their enormous bulks along #. banks of the streams. Other wild animals, not marked by so huge a size, distinguish themselves by power and fierceness. The lion and the tiger extend little beyond the torrid zone. The same may be said of the leopard, the panther, the ounce, and the hyaena. This zone produces also animals of striking beauty, and of a gentle and harmless disposition; such are the antelope, the zebra, and the cameleopard. It is still more advantageously characterised by an eminently useful species, that of the camel and dromedary, without whose services vast tracts of land in this zone would be wholly uninhabitable; and to which may be added, in the New World, the lama and the vicuna.' The wild beasts of temperate climes are but of two kinds, the wolf and wild boar; while here are reared in their highest perfection the horse and all the domestic tribes. In the higher latitudes, the ox, sheep, &c., are stunted in their growth, and gradually disappear, and give place to the elk, the sable, the ermine, and other well furted animals. The most valuable animal in these climes, perhaps, is the rein-deer, devoted to most of the occupations of the horse and ox of the temperate zone. The dog has been observed to be the faithful companion of man in all climates; but as he
approaches the equator, on the one hand, he loses his noble voice and bark; while on the other, in Kamtschatka, or even when removed from a temperate to a frozen clime, he assumes a new and thicker covering. Some of the different species of fox are said also to be found almost every where. 5. Of the vegetable productions of the earth.The geography of plants has been ably illustrated by modern writers, among whom baron Humboldt is, as in many other branches of science, most conspicuous. He considers the species of plants at present known, to amount to 44,000. Of these 6000 are cryptogamous. The remaining 38,000, phanerogamous plants, are distributed in the following manner: viz.
In Europe - - - - 7,000 — the temperate regions of Asia 1,500 – Asia within the tropics, and islands . 4,500 — Africa . - - - - . 3,000 – both the temperate regions of Ame
rica - - - - . 4,000 — America between the tropics . 13,000 — New Holland and the islands of the
Pacific - - - - 5,000
In the Prolegomena to his Nova Genera et Species Plantarum, M. Humboldt states that the proportion of plants which grow in latitudes 0°, 45°, 68°, are as the numbers 12, 4, 1. The mean annual tempereture in these regions is 81}”, 55}*, 32}*; the mean summer temperature 82}”, 70°, 53°. Within the tropics, the monocotyledinous plants are to the dicotyledinous, as one to six. Between the latitudes 36° and 52°, as one to four; and at the polar circle as one to two. In Germany the monocotyledinous plants are to the whole phanerogamous plants as 1 to 4}; in France as 1 to 43ths. The same proportion seems to hold good in North America.
Our author, in the spring of 1816, read to the French Institute, an important paper on the Distribution of Vegetable Forms; on which we shall now mainly rely. “The vegetables, he remarks, “which cover the surface of the globe present, when studied by natural classes, or families, striking differences in the distribution of their forms. It is to the laws of this distribution that I have recently turned my attention. On limiting them to the countries where the number of the species is exactly known, and dividing this number by that of the glumaceae, the leguminous plants, the labiated, and the compound, we find numerical relations, which form very regular series. We see that certain forms become more common from the equator towards the poles, like the ferns, the glumaceae, the ericineae, and the rhododendrons. Other forms, on the contrary, increase from the poles to the equator, and may be considered in our hemisphere as southern forms: such are the rubiaceae, the malvaceae, the euphorbia, the leguminous and the composite plants. Finally, others attain the maximum in the temperate zone. and diminish towards the equator and the poles. Such are the labiated plants, the amentaceae, the cruciferae, and the umbelliferae. In the planes of the torrid zone, the cruciferae and umbelliferae almost entirely disappear.
In considering the manner in which numerous fainilies of plants are distributed over the equatorial, temperate, and frigid zones, this writer further observes, that the vegetable forms present constant relations under the same isothermal lines. The grasses form in England a twelfth, in France a thirteenth, in North America a tenth of all the phanerogamous plants. The glumaceae form in Germany one-seventh; in France oneeighth; in North America one-eighth ; in New Holland, according to the researches of Brown, also one-eighth of the known phanerogamous lants. The composite Fo rather increase in the northern parts of the transatlantic continent; for, o: to the new Flora of Pursch, there is between the parallels of Georgia and Boston one-sixth ; in France one-seventh, and in Germany one-eighth, of the total number of species which are endowed with a visible fructification. In the whole temperate zone, the composite plants and the glumaceae together constitute nearly one-fourth of the phanerogamous class; the glumaceae, the compositae, the cruciferae, and the leguminosae together, nearly onethird. The last two classes, therefore, form the difference between one-third and one-fourth, which is one-twelfth of the whole flowering class. “It results from these researches, that the forms of organised being have a mutual dependance upon each other, and that the unity of nature is such that the forms are limited, according to constant laws of determination. When, upon any point of the globe, we know the number of species presented by one of the great families of the glumaceae, the compositae, the cruciferous, or the leguminous plants, both the whole number of phanerogamous plants, and the number of species that compose the other vegetable families, may be estimated with considerable accuracy. Thus, by knowing the number of cyperaceae, or composite plants, under the temperate zone, we may approximate to that of the graminous or leguminous plants in the same regions. The differences between the relations exhibited in the central parts of Europe, and the same latitude in North America, are accounted for by the different temperatures of these regions. The Flora of North America is a mixture of several Floras. The southern parts give it an abundance of malvaceae and composite plants; the northern regions, being colder than the same latitudes of Europe, furnish to this Flora numerous rhododendrons, amentaceae, and coniferae. The caryophylleae, the umbelliferae, and the cruwiferae are in general more scarce in North America, than in the temperate zones of the old continent. These constant relations observed on the surface of the globe, in the plains from the equator to the poles, are again traced in the midst of perpetual snows on the summits of the mountains. On the Cordilleras of the torrid zone the northern forms, in general, become more frequent. Hence it is that the ericineae, the rhododendrons, and the graminous plants, prevail at Quito, and on the summits of the Andes. On the contrary, the labiatae, the rubiaceae, malvaceae, and the euphorbiaceae, become as rare as in Lapland. This analogy, however, is not supported in the ferns, and the composite plants.
The latter abound on the Andes, but the former #. disappear, above the height of 1800 athoms. Thus the climate of the Andes resembles that of the north of Europe, only with respect to the mean annual temperature. The heat of the different seasons is very different, and exercises great influence on the phenomena of the vegetable kingdom. In general the forms which prevail among the Alpine plants are, according to my researches, under the torrid zone, the gramineae, the composite, and the caryophylleae; under the temperate zone, the compositae, the caryophylleae, and the cruciferae; and under the frozen zone, the caryophylleae, the ericineae, and the ranunculaceae.’ M. Humboldt delineates the distribution of plants at different altitudes in the torrid, tem| ". and frigid zones, according to our plate. he names of the plants are placed at the heights at which they cease respectively to grow. The numbers mark the annual temperature, according to the centigrade scale: those between brackets indicate the temperature of August. o: fathom is six French feet—6-394.53 Englist. eet. Upon the question whether there are plants common to the new and old world; he concludes, that many of the mosses and lichens are to be found both in the equinoctial regions of America and in Europe. But the case is not the same with the vascular agamae as with the agamae of the cellular texture. The ferns and the lycopodiaceae do not follow the same law as the mosses and the lichens. The former, in particular exhibit very few species universally to be found; and the examples cited are frequently doubtful. In reference to phanerogamous plants, with a few exceptions, the law of Buffon seems to be correct as to the species furnished with two cotyledons. It is not true that the ridges of the Cordilleras of Peru, where the climate is analogous to that of France, or Sweden, produce similar plants. The oaks, the pines, the yews, the ranunculi, the rose trees, the draba of the Peruvian and Mexican Andes, have nearly the physiognomy of the species of the same genera of North America, Siberia, or Europe. But all these Alpine plants of the Cordilleras, without excepting one among 3000 or 4000 that have been examined, differ specifically from the analogous species of the temperate zone of the old continent. In general, in that part of America situated between the tropics, the monocotyledinous plants alone, and the cyperaceae and the gramineae, almost exclusively, are common to the two worlds. These two families form an exception to the general law. M. Humboldt has given in his Prolegomena a catalogue of the plants common to the shores of the Orinoco, Germany, and the East Indies; the number of which does not exceed twenty-four species. The gigantic growth of timber in the new continent has already been noticed by us. See AMERICA, North. There are said to be 137 species in North America, whose trunks exceed the height of thirty feet, while in Europe scarcely forty-five species reach that height: but no firs are to be found in the mountains of South America, between the tropics. In temperate zones the same species of plants frequently grow together in clusters; but in the torrid zone the woods are formed of a much greater variety of trees. ‘The vegetable forms near the equator, says baron Humboldt, “are in general more majestic, more inposing; and the varnish of the leaves is more brilliant. The largest trees are perpetually adorned with flowers larger, more beautiful, and more odoriferous, than herbaceous plants in the temperate zone.'
OF TECHNICAL OR ARTIFICIAL GEOGRAPHY. Our preceding divisions have placed all the great natural features of this science before the reader. Geography, technically considered, teaches the doctrine of the figure, magnitude, and motions of the earth; of the various lines, parallels, climates, zones, &c., with which those who have systematised the science have supposed its surface to be diversified; the nature of latitude and longitude, and different positions of the sphere, &c.
SECT. I.-OF THE FIGURE AND MAGNITUDE of The EARTH.
The earth is a planet moving round the sun in an orbit nearly circular, and completing its revolution in the course of a year; at the same time it revolves continually upon its own axis, which is inclined to the plane of its orbit at an angle of sixty-six degrees and a half; the time of a revolution being twenty-three hours and fifty-six minutes. The revolution of the earth round the sun is called its annual motion, and the rotation it performs on its own axis is called its diurnal motion. While the earth revolves round the sun in the course of its annual motion, its axis, round which the diurnal motion is constantly performed, moves always parallel to itself. It is by the parallelism of the axis, and the annual motion of the earth, that the changes of the seasons are produced, while by the diurnal motion all places on the earth's surface are alternately turned towards the sun, and by these means the changes of day and night follow. When the earth was once known to be spherical, the curiosity of man would naturally lead him to endeavour to measure its dimensions; and we accordingly learn from history that such attempts were made. But the first accurate admeasurement that was made of the earth, of which we have any certain knowledge, was that executed by M. Picard, in France, towards the end of the seventeenth century, and which has been since several times verified. It is not difficult to understand in what way the earth may be measured. The direction of gravity is always perpendicular to the earth's surface; hence it follows that the zenith of any place, or point of the heavens directly over our head, and also the horizon, which is a plane touching the earth's surface at that place, will be continually changing according as we change our position on the earth's surface. It follows -ecordingly, that, as we travel from south to north, the pole of the heavens (or that point in "he heavens, in which the earth's axis when produced meets the sphere of the fixed stars) will
be more and more elevated above the horizon; the meridian altitude also of the stars in the northern regions of the heavens will appear to increase; while that of the stars in the southern quarter will be diminished. By the elevation or depression of the stars, we shall know the angle formed at the point of concourse of perpendiculars drawn to the earth's surface at each extremity of the terrestrial arc; for this angle is equal to the difference of the meridian altitude of the same star as seen from the extremities of the arc, diminished by the angle which the arc itself subtends as seen from the star; which last angle is altogether insensible. The number of degrees in the arc being found, it is only necessary to determine its length in some known measure, as a fathom, &c.; but, as it would be a work of great labor to apply a measure to an arc of great extent, it will be sufficient if its extremities be connected by a series of triangles to those of a base line of 3000 or 4000 feet in length; and, considering the accuracy with which the angles of these triangles can be observed, the length of the arc may be found with great precision. It is in this way that degrees of the meridian have been repeatedly measured. In France, for example, about 1793, an arc was measured extending from Dunkirk to Barcelona (for the purpose of settinga universal standard of weights and measures); and the degree whose middle is situated in lat 45° was by this means found to be 57,029 toises. Although the spherical figure is the most simple, and it is natural for man to suppose objects to be of that form which he most readily conceives, yet the simplicity of nature is not always measured by that of our conceptions. Infinitely varied in her effects, Nature is only simple in her causes; and her economy consists in producing a great number of phenomena, often the most complicated, by means of a few general laws. The figure of the earth is a result of these laws, which, modified by a great variety of circumstances, may cause it to deviate sensibly from a spherical figure; and certain small variations repeatedly observed in the length of degrees of the meridian, sufficiently indicate that such a deviation exists. The Academy of Sciences in France, in which this question has been warmly agitated, concluded with reason, that the difference of magnitude in the degrees of the meridian, if real, would be most sensibly perceived by the comparison of degrees measured at the equator and towards the poles. Accordingly a company of academicians was sent to the equator, where, having measured a degree of the meridian, they found it to contain 56,753 toises; which was shorter by 274 toises than a degree in lat. 45° north. Other academicians were sent to the north, and having measured a degree of the meridian in Lapland, about the latitude of 66° 20', they found it to be 57,458 toises, which was greater than the degree at the equator by 685 toises; and by these measurements it was completely proved, that the earth was not exactly spherical; and other measurements of degrees made since that period have all tended to show, that the degrees of the meridian gradually increase from the equator to the poles.
The ellipse is the next curve in point of simplicity to the circle, and the earth has been considered as a spheroid formed by the revolution of an ellipse about its lesser axis: its oblateness or compression in the direction of its poles, is a necessary consequence of the observed increase of the degrees of the meridian from the equator to the poles. For the radii of these degrees being in the direction of gravity, they are by the law of the equilibrium of fluids perpendicular to the surface of the ocean, with which the earth is in a great measure covered. They do not therefore, as in the sphere, tend to the centre of the spheroid; neither are they in the same direction, nor of the same magnitude, as the radii drawn from the centre to its surface; which cut it obliquely every where, except at the equator and poles. The point at which two adjoining perpendiculars, situated under the same meridian, meet each other, is the centre of the small terrestrial arc which they comprehend between them. If this are were a straight line, these perpendiculars would be parallel; or they could only be considered as meeting at an infinite distance; but, in proportion as this arc became curved, they would meet at a distance so much the less, as the curvature of the arc was the greater. Hence it follows, that seeing the extremity of the lesser axis is the point where the curvature of the ellipse is the least, the radius of a degree at the [. and consequently that degree itself, must e the greatest of any degree on the earth's surface. On the contrary, at the equator, or at the extremity of the greater axis, the curvature is the least, and therefore the degree in the direction of the meridian is there the smallest. And, in going from the equator to the pole, the degrees increase in such a manner, that, if the ellipse be not very eccentric, the increase is nearly proportional to the square of the sine of the latitude.
If the earth were exactly an oblate spheroid, its magnitude, as well as the proportion of its axes, might be determined by the mensuration of two degrees in the direction of the meridian. It should also follow, that by a comparison of all the degrees hitherto measured, taken two and two, we should obtain the same proportion between the axes. This, however, has not been the case. The results have indeed shown, that the earth is flattened at the poles; but they have left an uncertainty as to the quantity of the compression, extending from between the 170th to the 330th part of the radius of the equator. Between these two quantities, the former of which is nearly double of the latter, most of the results are placed; but in such a manner, that those most entitled to credit are much nearer to the least extreme than to the greater.
In consequence of this disagreement in the result of comparisons of degrees of the meridian, measured in different latitudes, it has been concluded by mathematicians, that the figure of the earth is not that of a spheroid; nor does it even appear, that the parts of it on each side of the equator are exactly similar.
It will, however, be sufficient for the purposes of geography, to suppose the earth a spheroid. Upon this hypothesis, La Place, by a comparison of the arc of the meridian measured at the equator, and another measured between Dunkirk and
Mountjoy, has found, that the polar diameter is less than the equatorial by 1-334th of the latter; and that a fourth part of the elliptic meridian is 5,130,740 toises; the toise being that used in measuring the earth in Peru, and reduced to a temperature of sixteen degrees and a quarter of a mercurial thermometer, divided into 100. degrees from the freezing point to that of water, boiling under a pressure equivalent to a column of mercury seventy-six centimetres in height, or about thirty inches English measure. This determination also agrees nearly with the results. from the combination of a great number of experiments, made at different places of the earth, upon the pendulum. Because the measure of a degree at the equator has been assumed, in the preceding calculation, at 56,753 toises, it follows that the equatorial diameter is 3,271,267, and the polar diameter 3,261,471 toises; the difference between them being 9796 toises. From these data, and the rules of mensuration, it will be easy to find the surface, solidity, &c., of the earth, also the number of iniles in a degree, &c. The following table of the dimensions of the earth is by Dr. Hutton :
The diameter . 79,579; miles.
SECT. 2.-OF THE CIRCLEs supposed to be Described on the EARTH's staf Ace.
In geography the circles which the sun apparently describes in the heavens, are supposed to be extended as far as the earth, and marked on its surface. In like manner we may imagine as many circles as we please to be described on the earth, and their planes to be extended to the celestial sphere, till they mark concentric ones on the heavens. The most remarkable of those supposed by geographers to be described in this manner are the following:— 1. The aris of the earth, or that imaginary line sing through the earth's centre, round which it continually revolves from west to east. 2. The poles, or points at which the axis meets the earth's surface. One of these is called the north-pole, and the other the south. These correspond to the poles of the heavens, or the points where the earth's axis, when produced, meets the starry sphere. 3. The equator, a great circle on the earth's surface, equally distant from both poles, and corresponding to the equinoctial circle in the heavens. It divides the earth's surface into two equal portions, called the northern and southern hemispheres. The equator is also sometimes, called the line or equinoctial line. The distance of any place, northward or southward, from the equator, is called its latitude, and is reckoned in degrees and minutes, &c. The distance between the poles and equator, which is a quadrant of a great circle passing through the poles, has by all geographers hitherto been supposed to be divided into ninety degrees; and each of these again subdivided into sixty minutes, &c. But some French astronomers, and in particular La Place, in his Exposition du Systeme du Monde, as well as in his Traité de Mecanique Celeste, has adopted the decimal division of the meridian. They have supposed the distance between the equator and the poles to be divided into 100 degrees, and each degree to be subdivided into 100 minutes, each minute into 100 seconds, and so on. All places lying on the north side of the equator are said to have north latitude; on the contrary, all places on the south side of the equator are said to have south latitude. Parallels of latitude are lesser circles upon the earth's surface parallel to the equator. They may be considered as indefinite in number; all places that lie directly east or west from each other are said to lie in the same parallel of latitude. The tropics are two lesser circles on the earth, parallel to the equator, and twenty three degrees and a half distant from it. That which lies on the north side of the equator is called the tropic of Cancer; and that which lies on the south side is called the tropic of Capricorn. These circles correspond to the circles of the same name, which limit the sun's north and south declination from the equinoctial in the heavens. The polar circles are two lesser circles upon the earth's surface, parallel to the equator. They are as far distant from the poles, which they surround, as the tropics are from the equator. That which lies towards the north pole is called the arctick circle, and that which lies next to the south pole is called the antarctick circle. To these there are corresponding circles, bearing the same names, in the heavens. Great circles passing through the poles of the earth, and therefore perpendicular to the equator, are called meridians. The meridian passing through any particular place lies in the plane of the celestial meridian of that place. It also divides the surface of the earth into two equal portions, called the eastern and western hemispheres, in j. of that place. The meridians may be considered as indefinite in number; and all places lying directly north and south from each other are upon the same meridian. Sometimes by the meridian of a place is understood the half of a great circle, passing through that place, and extending from the one pole to the other; and the other half of the circle is called the opposite meridian. If we suppose twelve great circles, one of which is the meridian of a given place, to intersect each other at the poles of the earth, and divide the equator into twenty-four equal parts, these are the hour or horary circles of that place. These are by the poles divided into twenty-four semicircles, corresponding to the twenty-four hours of the day and night. The distance between each two of these semicircles is 15°, being the twenty-fourth part of 360. The longitude of any place on the earth is an arc of the equator intercepted between the meridian passing through that place and some other meridian previously agreed upon which is called the first meridian. The longitude is reckoned eastward and westward from the first meridian, by which means all places lying in the hemisThere to the eastward of that place, through which the first meridian passes, will have east
longitude; and all places lying in the heinisphere to the westward of that place will have west longitude. Geographers at different periods, and in different countries, have fixed upon different places for the first meridian. The rule among the ancients was to make it pass through the place farthest to the west that was known. But the moderns, knowing that there is no such place on the earth as can be considered the most westerly, have laid aside that method of reckoning the longitude. Ptolemy assumed the meridian that passes through the farthest of the Canary o as his first meridian. After him, as more countries were discovered in that quarter, the first ineridian was removed farther off. The Arabian geographers fixed the first meridian #. the utmost shore of the western ocean. men again it was fixed at the island of St. Nicholas, near Cape Verd; then at the isle of St. James; and by Mercator at the isle Del Corvo one of the Azores, because there the magnetic needle pointed due north at that time. The Dutch fixed upon the Peak of Teneriffe as their first meridian, when it was considered the highest mountain on the globe; and the French, by order of Louis XIII., on the island of Ferro, one of the Canaries. In Great Britain, we reckon the longitudes of places eastward and westward fron the royal Observatory, Greenwich, and the United States of America adopt the same meridian. The differences of longitude between the last-mentioned meridians, all of which are occasionally referred to, or constantly used by geographers, is as follows (from Greenwich Observatory):—
The horizon of a place is either sonsible or rational. The sensible horizon of any place is a circle of the sphere, the plane of which touches the spherical surface of the earth at that place. The rational horizon is a great circle of the sphere, the plane of which passes through the centre of the earth, and is parallel to the plane of the sensible horizon. This horizon divides the celestial sphere into two equal portions or hemispheres; one of these is visible, but the other, by reason of the interposed body of the earth, is invisible. By the sensible horizon of a place is also sometimes understood a circle, which determines the segment of the surface of the earth, which is visible to the eye; called also the visible horizon. It is evident that this circle will be most accurately defined at sea, and equally distant every where from the eye of an observer, but below the level of his eye. It will also be so much the more extensive, as the eye is raised above the earth's surface. The zenith of a place is the point of the heavens directly over the head of an observer; and the nadir is the point in the oppposite hemisphere, directly under his feet; or the zenith and nadir are the poles of the horizon. Great circles of the sphere passing through the zenith and nadir are called vertical circles, or azimuths. They are also sometimes oulled secondaries of the horizon; and in general any