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in the Thian Shan range, at a distance from the sea at which they are nowhere else to be met with.
The highland of Asia is distinguished by possessing the loftiest elevations. They are piled up in close vicinity to the sultry tropical plains of Hindostan, in the snowy chains of the Himalaya, and reach their culminating points in the peaks of the Dhawalagiri and Kinchin-ginga. Though, according to the latest report of Dr. Hooker to A. von Humboldt, Kinchin-ginga attains a height of 28,176 feet, which exceeds that hitherto assigned to Dhawalagiri by 176 feet, yet at the same time it has been conjectured that a new measurement would maintain Dhawalagiri in his previous rank.
The mean pressure of the atmosphere at the surface of the sea is generally estimated as equal to the weight of a column of mercury of 30 inches in height, which is about 15 pounds on the square inch of surface, and is equivalent to à column of water of nearly 34 feet in height. The oxygen alone is equal to a column of 7.8 feet of water over the whole earth's surface, from which an idea may be formed of the immense quantity of that element, and how small the effect must be of the oxidating processes observed at the earth's surface in diminishing it. If the atmosphere were of uniform density, its height, as inferred from the barometer, would be 11,000 times 30 inches, or 5.208 miles; but the density of air being proportional to the pressure upon it, diminishes with its elevation, the superior strata being always more rare and expanded than the inferior strata upon which they press.
At a height of 2.7 miles the atmosphere is of half density, by calculation, or 1 volume is expanded into 2, and the barometer would stand at 15 inches; the density is again halved for every 2.7 miles additional elevation. From calculations founded on the phenomena of refraction, the atmosphere is supposed to extend, in a state of sensible density, to a height of nearly 45 miles. It is certainly lirsited, probably from the expansibility of the aërial particles having a natural limit. The atmospheric pressure also varies at the same place, from the effect of winds and other causes, which are not fully understood. Hence the use of the barometer as a weather glass ; for wet and stormy weather is generally preceded by a fall of the mercury in the barometer, and calm and fair weather by its rise.
The temperature of the atmosphere is greatest at the earth's surface, and has been observed to dininish one degree for every 352 feet of ascent in the lower strata. It is believed, however, that the progressive diminution is less rapid at great distances from the earth. But at a certain height the region of perpetual congelation is attained even in the warmest climates; the summits of the Andes, which rise 21,000 feet, being perpetually covered with snow under the equator. The line of perpetual congelation, which has been fixed at 15,207 feet at O latitude, descends progressively in higher latitudes, being 3,818 feet at 60°, and only 1,016 feet at 75o. The decrease of temperature with elevation in the atmosphere is ascribed to two causes. 1. To the property which air has of becoming cold by expansion, which arises from an increase of its latent heat with rarefaction. The actual temperature of the different strata of the atmosphere is indeed believed to be that due to their dilatation, supposing that they had all the same original temperature and density at the lowest stratum. 2. To the circumstance that the atmosphere derives its heat principally from contact with the earth's surface. The sun's rays appear to suffer little absorption in passing through the atmosphere; but there are some observations on the force of solar radiation which are not easily reconciled with that circumstance. A thermometer, of which the bulb is blackened, rises a certain number of degrees above the temperature of the air, when exposed to the sun, but the rise is decidedly greater on high mountains than near the level of the sea, and in temperate or even arctic climates, which is more remarkable, than within the tropics. It is a question how solar radiation is obstructed in the tropics.
The blue colour of the sky has been found by Brewster to be due to light that has suffered polarization, which is therefore reflected light, like the white of light clouds. The air of the atmosphere must therefore have a disposition to absorb the red and yellow solar rays, and reflect the blue rays. At great heights, the blue colour of the sky was observed by Theodore de Saussure to become deeper and deeper, being mixed with black, owing to the absence of white reflecting vapour or clouds. The red and golden tints of clouds appear to be connected with a remarkable property of steam observed by Professor J. Forbes. A light seen at night through steam issuing into the atmosphere from under a pressure of from 5 to 30 pounds on the inch, is found to appear of a deep orange red colour, exactly as if observed through a bottle containing nitrous acid vapour. The steam when it possesses this colour is mixed with air, and on the verge of condensation; and it is known that the golden hues of sunset depend upon a large proportion of vapour in the air, and are, indeed, a popular prognostic of rain.—Thomas Graham.
LESSON XXVIII.- WEDNESDAY.
THE DISCIPLES AT EMMAUS.
It happen'd on a solemn eventide,
And ask'd them, with a kind engaging air,
Now theirs was converse, such as it behoves
may be found, that harbour at this hour That love of Christ, and all its quickening power,
And lips unstain’d by folly or by strife,
ENGLISH HISTORY-THE COMMONWEALTH. Immediately after the death of the king, the remnant of the House of Commons decreed the abolition of monarchy in England, declaring it treason to proclaim the Prince of Wales, or any other person, successor to the throne. The House of Lords was suppressed, and a Council of State, consisting of forty-two persons, appointed. Some royalists of rank were brought to trial, and three of them, the duke of Hamilton, and Lords Holland and Capel, were beheaded.
The authority of the new republic was, however, far from being undisputed. Ireland declared for Charles II., and Scotland promised him allegiance, on condition of his taking the “Solemn League and Covenant.” To remedy this state of affairs, Cromwell was appointed lord lieutenant, and sent to Ireland, with a small but resolute army. In a few months the cause of the royalists , was rendered desperate, and the country so far subdued as to enable the English general to turn his arms against Scotland, where the young prince had lately landed, and was impatiently enduring the rigid restraints imposed by the Presbyterian leaders. By the victory of Dunbar, Cromwell reduced to submission the whole country south of the Forth, Edinburgh and Leith opening to him their gates. The commu