Page images
PDF
EPUB

has become a fit receptacle for the varied forms of animal and vegetable existence with which we see it so profusely stored.

The variable distribution of heat has produced a striking effect in modifying the earth's surface. The cold of the polar regions covers them at all seasons with an extensive deposite of snow and ice, the margins of which are periodically dissolved by the increasing warmth of summer, to be repaired during the succeeding winter. The numberless icebergs, originally formed on the land or in its vicinity, floating on the ocean, and drifted by winds and currents, often pass into more genial regions, producing occasional variations of temperature. The elevated ridges of mountains experience a similar degree of cold, and in all climates, even in the torrid zone, are covered towards their summits with perennial snow.

Limited as are our powers of examining the interior of the globe, we yet find in its crust indications of a power which, by operating so as to produce apparent confusion, has effected results highly beneficial to the beings by whom the earth has been peopled. The strata, at first regularly superimposed upon each other, and consisting of those diversified materials which are supplied by the disintegration of pre-existing rocks, have been broken up, and inclined in every possible degree, so as to form those depressions and elevations which we every where observe on the surface. These inequalities have been increased by the protrusion of masses from the more central regions, and the whole has been sub jected to the agency of powerful currents of water, by means of which the angular cavities and projec

tions have been smoothed or filled up. The consideration of these phenomena constitutes a distinct branch of natural science.

The mountains, rocks, and strata, are composed of ingredients which in themselves are worthy of examination, and capable of affording intense interest. The extremely-diversified forms which these substances assume, their various properties, their uses in the economy of nature, and the purposes to which they may be applied by man, render their investigation not less useful than pleasant.

A most extensive and delightful field of observation presents itself to us in the vegetable bodies with which the surface of the land, and even the depths of the ocean, are so profusely furnished. The various regions of the globe are not less characterized by the form and grouping of the plants which have been allotted to them, than by the comparative activity of their vegetating power. The wastes of Europe, covered by ling, heaths, rushes, and sedges, exhibit little change of aspect under the variations of temperature and the revolutions of the year; while the plains of Venezuela, which during the drought are covered with a layer of sand, and present only a few withered palms scattered along the margins of muddy pools, are converted in the rainy season into an ocean of luxuriant vegetation. In the equinoctial regions of the globe, palms, arborescent ferns, and a multitude of magnificent trees, intertwined with flowering lianas hanging in festoons, form themselves into impenetrable forests, whereas the frigid regions of the arctic circle hardly produce plants a foot in height. The solemn and stately pines of the north of Europe have a very different

aspect from the slender-twigged beeches and chestnuts of its temperate regions, or the laurels and fanpalms of its southern shores.

Viewed in relation to their productions, the gelid regions of the globe are not confined to the circumpolar zone, but extend along the summits of the lofty mountains, following the line of perennial snow, which rises from the level of the sea, in Greenland and Spitzbergen, to the height of 14,000 feet in the Andes. These steril tracts nourish only a few species of plants, although the individuals belonging to them are frequently numerous. In the valleys, and on the southern slopes, no sooner has the returning heat of summer melted the snow, than a beautiful carpeting of verdure, diversified by flowers of various tints, spreads over the soil, displaying an astonishing rapidity of development, while the rocks in many places appear covered with cryptogamic plants. Besides mosses, lichens, and other inferior tribes, multitudes of ferns make their appearance. Grasses and creeping dicotyledonous plants are fully matured; and a rich pasturage affords, during the warm season, abundant nourishment to herbivorous animals. Some trees of small size also appear here and there, or even form themselves into thickets and woods. But, in general, the vegetation of these dreary regions, placed on the limits of the habitable earth, is characterized by a paucity of species and a stunted growth.

Firs and pines, existing in vast numbers, and retaining a perpetual though gloomy verdure, characterize the transition from the frigid to the northern temperate zone. This last extends from the parallels of 50° to 40° north latitude, and in its southern borders, the beech, the lime, and the chestnut, mingle

with the trees peculiar to more southern regions. The meadows and pastures, especially those in the vicinity of the sea and in the mountain-valleys, are clothed with a brilliant verdure, which we in vain look for in the other sections of the globe.

The warm temperate zone, extending to 25°, presents in general a less beautiful vegetation; for although the heat is greater the humidity is less constant. But it is in the torrid latitudes that Nature displays all her magnificence. There the species of tribes, which in other climates are herbaceous, become shrubs, and the shrubs trees. Ferns rise into trunks equal to those of pines in the northern regions of Europe; balsams, gums, and resins, exude from the bark; aromatic fruits and flowers abound; and the savage, as he roams the woods, satisfies his hunger with the spontaneous offerings of the soil. Here also are all the climates of the globe, and almost all their productions united; for, while the plains are covered with the gorgeous vegetation of the tropics, the lofty mountains display the forms that occur in the colder regions, and the places intermediate in elevation all the graduated transitions from these to the warmest parallels.

The vegetation of the seas presents much less diversity than that of the land. It is less luxuriant, less elegant, less ornamented, and less productive of substances directly useful to man. There is also less distinction between marine plants of different latitudes; for the great currents of the ocean, and other causes, render its temperature more equable than that of the atmosphere.

The numerous and diversified forms which plants assume, their distribution over the globe, their

various qualities and uses, and their internal organization, are subjects which have long occupied the attention of observers. In their reproduction, growth, and maturation, phenomena are presented to us, which are well calculated to excite our admiration; and the curious and diversified apparatus of tubes and cells, in which are circulated the fluids derived from the atmosphere and the earth, although apparently more simple than that of the animal economy, affords a profound as well as an interesting subject of research.

All parts of the earth's surface, even the deep recesses of caves and mines, the snows of the polar and alpine regions, and the bottom of the sea, are more or less covered with plants. The same may be said respecting animals, which, being much more diversified in their forms and internal structure, and endowed with more wonderful faculties, lead the mind, by the contemplation of their mechanism and habits, to a nearer approach to the great Creator of all things.

From the gigantic elephant that roams among the splendid forests of the warmer regions of the earth, the unwieldy hippopotamus that plunges in the pools and marshes of the African wilds, and the timid and graceful giraffe that bounds over the sandy desert, down to the little dormouse that we find slumbering in its winter retreat, to the lemming that in congregated myriads overruns the fields of the North, or to the mole that burrows under our feet, we find an astonishing variety of beings, exhibiting forms, instincts, passions, and pursuits, which adapt them for the occupation of every part of the globe. The woods, the plains, the

« PreviousContinue »