temperature indicated was 75.5°, while that of the country is 50°; and consequently the increase of heat there is at the rate of 1° for every 54 feet.

At Giromagny, in the Vosges, the annual temperature at the surface is 49°; at 330 feet depth it is 53.6°; at 1008 feet, 65.8°; at 1416 feet, 74·6°.

In four of the deepest mines of Saxony the annual temperature at the surface is 46·4° ; at from 510 to 600 feet depth, it is 54.5°; at 840 feet, 58°; at 1080 feet, 62.6°.

In the deepest British coal mine, that of Killingworth, the annual temperature at the surface is 48°; at 900 feet depth it is 70°; at 1200 feet, 77°. A similar gradation is found in many of the deeper mines at home and abroad.

There is thus in the Vosges an increase of temperature in descent below the surface amounting to about 1° in every 60 feet; in Saxony 1° in every 66 feet; and in Britain 1° in every 45 feet. After the ratio observed in the Vosges, the temperature of the hot springs at Bath, 113°, will be found at three-quarters of a mile in the interior of the earth, and that of boiling water at a depth of nearly two miles. "The facts strongly support three conclusions: First, that the heat of an interior shell of the earth is greater than the superficial shell. Second, that this heat augments progressively as we descend towards this region, in a ratio bearing some relation to the depth. Third, that, even at moderate depths, this heat is greater than the mean heat of the globe ought to be, if entirely derived from the sun. The heat of such an interior mass must be constantly diffusing itself towards the surface; and at the surface it may be kept down, so as to affect the temperature derived from the solar action very feebly, by the greater or less rapidity of its dissipation. But as it is very improbable that it should be diffused with perfect equality round the whole exterior shell of the globe, it may be the true source of some of those anomalies of climate, such as the discrepancy in the annual heat under the same parallel, which cannot be easily referred to other known causes." If the heat of the globe were entirely derived from the sun, Pekin, at an inconsiderable elevation above the sea, ought to have the same mean annual temperature as Naples, being under the same parallel of latitude; but instead of this being the case, the temperature falls short of that at Naples by nearly 9°. Other causes may contribute to produce this discrepancy; yet it is not unreasonable to suppose that the mean heat at Naples is raised by its proximity to a focus of internal heat which smokes and flashes through the chimney of Vesuvius.

No reference has yet been made to physical climate in the southern hemisphere, respecting which opinion has recently been considerably modified. The idea long prevailed that the whole region south of the equator had a much lower temperature than the northern side; but it is now sufficiently ascertained, that there is no discrepancy whatever in its equinoctial districts. The Isle of France has the same annual temperature, 80·1°, as Jamaica and St. Domingo, under a corresponding northern parallel. The mean temperature at Rio Janeiro is 74-5°, and at Havannah, at a similar latitude north, it is 76.4°. The amount of annual heat about the parallel of 34° of south and north latitude exhibits a remarkable equality, as appears from the following comparison :

Under the parallel of 51° 25′ south, the mean temperature of the Falkland Isles is 47.3° and at the same latitude north we find the mean temperature in Europe from 50°

to 51.8°, while in America it is scarcely from 35.6° to 37.4°. The annexed table contrasts temperatures observed at sea:

It may be concluded, therefore, that as far as 40° of latitude, the warmth of the southern hemisphere is equal to that of the northern, while, considering the Transatlantic climates apart from the Cisatlantic, it is certain that the mean temperatures of the year, within the bounds referred to, under the corresponding geographical parallels, are even greater in South than in North America. Beyond those limits the southern hemisphere appears to have a lower temperature than the northern. Hence large masses of ice descend towards the equator from the southern pole to a much greater distance than is the case in the northern seas. During the surveying voyages of the Adventure and

Beagle, along the south coast of South America, the glacier furthest from the pole, descending to the sea coast, was found in latitude 46° 50′, in the Gulf of Penas; but a few miles to the north of this glacier, in the Laguna de San Rafael, some Spanish missionaries encountered icebergs, in a narrow arm of the sea, on the 22d of the month corresponding with our June, and in a latitude answering to that of the Lake of Geneva ! According to Von Buch, the most southern European glacier which comes down to the sea is met with on the coast of Norway in latitude 67°. This is more than 20° of latitude, or 1230 miles nearer the North Pole than the Gulf of Penas is to the South. Mr. Darwin puts the occurrence of this glacier in the southern hemisphere in a striking point of view, by remarking, that it descends to the sea-coast within 74° of latitude, or 450 miles of a harbour, where three species of oliva, a voluta, and a terebra, are the commonest shells, within less than 9° from where palms grow, within 44° of a region where the jaguar and puma range over the plains, less than 240 from arborescent grasses, and, looking to the westward in the same hemisphere, less than 2° from orchideous parasites, and within 1° of tree-ferns! In South Georgia, an island discovered by Cook in his cruise of 1775, in latitude 53°, answering to the parallel which passes over the central counties of England, the eternal snows come down to the sea-shore, while the curve of perpetual congelation with us is at the height of more than 5000 feet. The perpetual snow does not descend to the sea-level on the north of the equator till we arrive at the parallel of 80°, which is twenty-seven degrees nearer the pole than the point where the same fact transpires in the southern hemisphere. This greater degree of cold was at first attributed to an astronomical cause- -that of the acceleration of the earth's motion in its perihelion, in consequence of which the sun is a shorter time, by nearly eight days, on the south, than on the north side of the equator. But the true cause is undoubtedly geographical, the great preponderence of the ocean in southern regions, which radiates less absolute heat than dry land, and contributes to diminish the annual temperature of that part of the globe. The same cause, however, operates to free the south-temperate zone from "excessive climates," or those violent seasonal contrasts of temperature which the AngloAmerican and the inhabitants of Pekin experience, mild winters alternating with cold summers. Port Jackson, in a latitude answering to that of Cairo, has the winter of that city, and the summer of Marseilles. In Van Diemen's Land, corresponding nearly in latitude to Rome, there is the summer of Paris and the winter of Naples.

We may now cast a general glance over different districts of the globe which present strongly-marked diversities of climate and productions, confining our attention chiefly to the northern hemisphere.

Equatorial and Hot Regions.-These occupy a zone extending on each side of the line to a few degrees beyond the northern and southern tropic. As before remarked, the mean temperature appears to be higher in situations verging towards the tropics than at the equator; and by this is to be understood the temperature of the air near the surface of the earth, as determined by a thermometer, protected from radiation and every kind of foreign influence. Thus the mean equatorial temperature is given by Humboldt at 814°; but at Pondicherry, in latitude 11° 55′ north, it is at least 85°. This is the region of the finest spices, the sugar-cane, the palm and banana tribes. It includes the islands and continent of Southern Asia, the middle and northern countries of Africa, and the central parts of America. In its level midland portions, frost and snow are unknown, and the uncivilised natives of various localities have often deemed the statement a fable of the Europeans, that rivers became solidified by cold. In the well-watered countries, the trees are covered with perpetual verdure, the fields exhibit a constant carpet of beautiful and odoriferous flowers, and the only season resembling winter is the season of rain; but after the rains, the heat occasions noxious exhalations from the fruitful soils, and espe

cially from the marshy districts, which originate formidable remittent and continued fevers, the well-known scourges of hot climates. The dry portions of this zone are sandy or stony wastes, with little or no vegetation except in a few oases, and with scarcely an animal besides the camel. Towards the tropics, the temperature is less equable than at the equator; the seasonal heat is excessive; and travelling, or any kind of exertion, through several hours of the day becomes impossible. The wooden furniture in dwellings warps and shrinks; glass is sometimes cracked; thirst is continual; the body is debilitated; all disposition to effort is destroyed; and motion often becomes painful. The sun-stroke, or coup-de-soleil, is the frequent consequence of exposure to the intensity of the solar action, and was fatal to numbers in the crusading armies, who, unaware of danger, encountered the fierce beams of mid-day on the plains of Syria.

Warm Regions.-These extend from the northern limit of the sugar-cane to the northern boundary of the olive and the fig; and include the southern districts of Europe, part of midland and south-western Asia, and portions of the southern United States. The frosts here are not severe in the plains; snow is also rare; and the rivers are seldom frozen over. The winters are more distinguished by dampness than cold, resembling the spring of the temperate regions. Vegetables on the south of this zone grow during seven or eight months in the year, and the trees are not stripped of their foliage more than two months. The air of the European warm regions is in general clear and salubrious; but, owing to the abundance of vegetation, and numerous marshes in corresponding transatlantic climates, noxious effluvia are continually formed. The autumns are uniformly sickly; and the countenances of the inhabitants have a pale and sallow cast, instead of the bloom and freshness which belong to those of more northern districts, or to the brunette of the southern Europeans.

Temperate Regions. This zone reaches from the northern limit of the olive and fig to that of the wine-grape, and has a mean temperature varying from 50° on the northern border to 59° on the southern. The transition from winter to summer is here gradual, and the four seasons are distinctly marked. The winter is commonly from three to five months long in the northern parts, attended with a considerable quantity of snow; and the waters are often strongly frozen. In the southern parts, the winter does not exceed two or three months; the fall of snow is less, and the frosts are seldom severe. Grain, vegetables, and many fine fruits are produced in abundance, with excellent pasturage, but the fruits often ripen with difficulty, and the harvests are injured by moisture and rains. France, Germany, and southern Russia are included in this region, with Holland, Belgium, England, and Ireland, on account of their maritime situation. The same climate characterises a part of the east coast of Asia, the northern and midland United States, the interior country south of Lake Huron, and the basin of the Columbia river, At Nootka Sound the rivers do not freeze until January; and at the mouth of the Columbia, the first frost observed by Lewis and Clark was in that month.

Cold Regions.-The country in Europe between the wine-grape and the northern limits of the oak, is included in this zone, or midland Russia and southern Scandinavia, with southern Siberia in Asia, and the British provinces in North America. The summers are short, hot, and oppressive, and the winters severe and protracted. Nearly six months in the year, the temperature of Stockholm and Petersburg is below the freezing point. The rivers are frozen during that period; the snow is permanent; and the wolf becomes dangerous to the traveller. The air, keen and penetrating, is remarkably clear, still, and salubrious. Where the ground is clear of timber, and level, the winter-picture is that of a frozen sea, which spreads for many a shining league, the sun often careering through the heavens cloudless from morn till night, and then giving place to the moon, soft, clear, and yellow, the rim strongly and beautifully defined on the

deep concave of the sky.

"There is something," observes the authoress of the spirited Letters from the Baltic, "very exhilarating in this breathless, still, bright cold-with a clean white expanse, a spotless world, before you-every tree fringed-every stream stopped-freedom to range over every summer impediment; while the crystal snow, lighting up into a delicate pink, or pearly hue, or glittering with the brightest prismatic colours beneath the clear, low sun, and assuming a beautiful lilac or blue where our long shadows intercept his rays, can no longer be stigmatised as a dead lifeless white." The thermometer is frequently several degrees below zero. The severity of the cold appears in icicles pendant from the eye-lashes of the Russian boor, and the conversion of his beard into a lump of ice from the congelation of the vapour of his breath. The most singular feature of this zone is the rapidity with which the change from winter to summer transpires, observable in Canada as well as in northern Europe. The spring is almost obliterated as a season. The snow melts, the hard-frozen ground is unlocked, and the rivers are unsealed with astonishing quickness; and a few days will suffice for the transition of the trees from wintry nakedness to the sprouting out of their full complement of leaves.

Frozen Regions. This zone extends from the northern boundary of the oak to the pole, and is of much narrower dimensions in Europe than in America and Asia. The birch, the hardiest of trees, generally ceases to grow about latitude 70° in Europe, where man is compelled to give up the cultivation of grain. Shrubs and bushes linger on farther north; grasses and lichens then are only to be met with; and eternal snows and ice succeed. In regions north of 59° in Asia, 71° in Europe, and 54° in America, the mean annual temperature is below the freezing point. In winter brandy and mercury freeze. Around Hudson's Bay and in North Siberia, lakes and standing waters of no great depth are frozen to the bottom; the inhabitants remain crowded together in small huts; and if the cold air suddenly enters a habitation, the vapours fall in a shower of snow. Notwithstanding the efforts of our enterprising countrymen, the central region of this zone, the geographical pole of the world, has not been reached, and consequently the mean temperature is yet a matter of surmise. From the different indications of temperature in high northern latitudes in the Old and New World, it has been inferred that the point of greatest cold is not coincident with the pole, but that the lowest temperature is found at two points situated at about 80° of latitude, and 95° east longitude, and 100° west. Captain Parry, who wintered at Melville Island, often observed the thermometer in the ship at 50°, and at a distance from the ship at 55° below zero, perhaps the lowest temperature, upon which entire dependence may be placed, that has been remarked. He wintered on the south coast of the island in about latitude 74°, and obtained the following results of observation :

:

These results indicate a very extraordinary degree of cold, far surpassing what had ever been supposed to exist in the imagination of the poets, or what the calculations of science formerly assigned to the pole itself, where the hoary desolations of the arctic regions were conceived to be concentrated. According to a table given by Leslie, the mean