forth into energy, expanded, invigorated and matured. If, as we have presumed to suppose, the revolution of 1688 may have had no small share in accelerating that progress of light which has dissolved the prejudices that supported despotism, they may be permitted, besides their exultation as friends of humanity, to indulge some pride as Englishmen.

It must be confessed that our ancestors, in 1688, confined, in their practical regulations, their views solely to the urgent abuse. They punished the usurper without ameliorating the government, and they proscribed usurpations without correcting their source. They were content to clear the turbid stream, instead of purifying the polluted fountain. They merit, however, veneration for their achievements, and the most ample amnesty for their defects; for the first were their own, and the last are imputable to the age in which they lived. The true admirers of the revolution will pardon it for having spared abusive establishments, only because they revere it for having established grand principles.—Sir J. Mackintosh.

LESSON L.-FRIDAY.

DAY AND NIGHT.-THE SEASONS..

The successive alternations of day and night arise from the perpetual motion of the earth on its axis, exposing certain portions of its surface to the solar presence, and withdrawing them from it. The unequal length of the days and nights is occasioned by the annual revolution of the earth round the sun with its axis inclined to the plane of its orbit. Suppose one of the poles had always pointed towards the sun, then notwithstanding the daily rotation and annual revolution, one half of the globe would have had constant day, and the other half constant night. Or, suppose the earth's axis had been perpendicular to the plane of its orbit, the equator always pointed directly towards the sun, light and darkness would have alternated for equal times on all parts of the globe.

The axis of the earth is inclined 233° from a line perpendicular to the plane of the orbit. It remains constantly parallel to itself during the annual revolution; and hence,

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except at the equator and the poles, and on the 21st of March and 23rd of September, when the sun is in the equinoctial, in all places the days and nights are of unequal length. To all places at the equator the days and nights are always of equal length. At the north pole, from the 20th of March to the 23rd of September, the sun is constantly above the horizon, and below it through the opposite interval. There is, therefore, through the year but one day and night, each of about six months' duration. This is the case also at the south pole; but inversely as to the period. In both instances, however, the length of the day is increased by refraction, which is very considerable in high latitudes, and causes the sun to be seen for several days before he comes above the horizon, and after he has sunk below it. The night also is relieved by long twilights, the play of the aurora borealis, and the strength of the moonlight as reflected by the snow.

The regular succession of the seasons which we experience, and the important benefits it confers, depend mainly upon the regular inequalities of the length of the days and nights, heightening or lowering the temperature of the earth according as the term of its exposure to the sun's rays is increased or lessened. At the winter solstice, or December 21, the northern hemisphere has its shortest day and longest night. The period of receiving heat from the sun is at its minimum, and the period of radiating, or losing the heat received, at its maximum; consequently, the temperature is low. From thence to the vernal equinox, or March 21, the days gradually lengthen and the nights shorten till both are of equal duration; and from thence to the summer solstice, or June 21, the days gain in length upon the nights, the temperature increasing, owing to the larger supply of the solar influence. From thence to the autumnal equinox, or September 23, the days are gradually reduced in length till they are again equal to the nights, and from thence to the winter solstice, the nights gain in length upon the days, the temperature decreasing.

The same effects transpire in the southern hemisphere, but in a contrary order. As we pass from summer to winter, from heat to cold, from long days and short nights

to long nights and short days, the inhabitants of the south temperate zone pass from winter to summer, from cold to heat, from long nights and short days to long days and short nights. On an average, with us, the temperature rises from January 5 to July 5, and falls from July 5 to January 5. It has been calculated, that were the sun in summer to remain ten days below the horizon, it would be enough to freeze every thing on the surface of the earth.

Summer heat and winter cold are also influenced by the physical state of the atmosphere at the two seasons. In summer the atmosphere is generally dry; but in winter it is loaded with vapours which considerably weaken the intensity of the sun's rays. Another and a very influential cause of summer heat and winter cold, is the diverse direction of the sun's rays at the two seasons. It has been calculated, that out of 10,000 rays falling upon the earth's atmosphere, 8,123 arrive at a given point if they come perpendicularly; 7,024 if the angle of direction is 50°; 2,831 if it is 7°; and only 5 if the direction is horizontal; the rest being absorbed and reflected. It can be demonstrated that the heating effect of a vertical sun is as great in eight hours as it would be in sixteen hours, his rays falling at an angle of 60°. Now as the sun has his least altitude in the heavens when the days are shortest, his rays falling most obliquely, and his greatest altitude when the days are longest, his rays then being most direct; these two causes mainly contribute to the different temperature of the two seasons—to the production of winter and summer.-Milner.

LESSON LI.-MONDAY.

HYDROGRAPHY.

An intermediate gradual descent is for the most part wanting in the American rivers; but their long course through the plains introduces oceanic influences far into the continent, and to the very foot of the high mountains. The South African rivers form a decided contrast to these, inasmuch as their longest course is on the high land, and is united with the very short portion of their course through the plains at their mouths, by a boisterous descent over

terraces; so that the influence of the ocean is limited to a narrow line of coast. The solitary river of North Africa, the Nile, seems also to be deficient in a transitional country, and is further characterised by the total want of tributary streams throughout the great length of its lower course. Pent in between deserts, millions of men have their history and even their existence chained to a solitary river artery, which could never have awakened civilized life in its valley, but for its inundations and its delta. In Asia, every river system has peculiarities of its own. The twin-rivers, Euphrates and Tigris, display a regular development of gradual descents; but the desert soil of their lower course confines their beneficial influence to a narrow tract. The Indus has a long upper course on the high land, a short intermediate passage through a wild valley, and a preponderating course in the lowland country. Its largest tributary on the left bank, the Sutlej, displays precisely similar proportions; but below the junction of the Sutlej, the Indus is again prevented, by the desert on one side, and an impenetrable mountain-wall on the other, from receiving those abundant supplies which, during the previous half of its lower course, had been sent to it by the Himalaya. The Ganges, as is so frequently the case in America, is destitute of the completeness derived from a transitional descent; while its brother stream, the Brahmapootra, displays the same series of descents as the Indus; but the united lowland of both, as far as their estuaries, is netted over by countless river arteries. The rivers of Hindostan are mostly plateau rivers, like those of South Africa; on the contrary, those of Further India, rising in a country little known to us, hurry through high and intermediate elevations, and separate, in proportion as they approach their estuaries, into numerous arms, that fertilize the plains of their lower course. The two principal Chinese rivers, Hoang-ho and Yan-tse-Kiang, exhibit an equally regular series of three descents, and water, in common, one of the most fruitful lowlands of the earth; but, in consequence of the great contrast between the countries in which they rise and those near their mouths, and the wild character of the intermediate valley, they are unable to fulfil the purpose of communication; and in this respect, most of the Asiatic rivers

which have their upper course in the interior of the great highland, are inferior to the European rivers. The Amoor has no level plain at its mouth; for the extent of its basin, it is in this respect solitary. The Siberian rivers flow but very partially through a threefold change of elevation; the more westerly they are, the more their lower course through the extensive lowland predominates, after the example of the rivers of South America; and all of them convey immense masses of water to the sea, by a lower meridional course, but into a polar sea, whose icy breath for many months overlays the water-courses far inland with a rigid covering, and checks every development of beneficial influence. The waters of the great inland basin display, according to their situation, more or less variety of successive descents. They are in themselves the more important, since life and cultivation cling to their course in the midst of the desert; but they fall short of a complete development, from the want of the important feature-communication with the open ocean.

LESSON LII.—TUESDAY.

THE MOON.

Of the objects of astronomical science, the moon is the second in splendour, the first in beauty. Its peculiar influence over our planet, its apparent magnitude and singular beauty, arise from its near vicinity to us. Near vicinity may seem an inappropriate term when applied to a body 200,000 miles distant. Relatively to our measurements and journeys within the narrow limits of the surface of our own globe, which circumscribe our personal knowledge, such a distance is immense; but, as compared with astronomical distances, it is short and inconsiderable. Let it be considered that we are more than ten times as distant from the more remote planets in our own system, as from the sun, its centre. Yet if we were travelling to the sun, and the moon were reached as the first stage of our progress, it would be but one of four hundred equally long. Then, as we have telescopes capable of magnifying one thousand times, the spectator of the moon through an instrument of that power, surveys the object as if but at a distance of two hundred