A Comparative View of the Mortality of the Human Species, at All Ages. Black William

Чтение книги онлайн.

      consists of the Sun, of seven Planets surrounded by ten or more Moons, and of the Comets. The other siderial lights with which the vault of Heaven is studded, and which are denominated Fixed Stars, have a very distant affinity with our planetary sphere: they are infinitely too remote to be enlightened by our luminary; and therefore astronomers, with good reason, imagine each star to be a sun to encircling planets, though invisible to us; and to constitute throughout boundless space thousands, or perhaps millions, of habitable worlds. Numbers of those stars, most luminous and proximate, are arranged into arbitrary clusters, called Constellations, or Signs; and serve to mark the several stages of the rotating orbs in our system.

The Sun, whose magnitude far surpasses that of the seven planets united, is placed in the center, suspended in the immense celestial expansion and firmament. Surrounding him, at different distances, and in the following order, are the planets Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Georgium Sidus. These planets are incessantly revolving from west-by-south to east, and within certain intervals of time, make a complete circle round the Sun; which is the length of each planet’s year; and is larger and longer in proportion to their respective distances. The velocity of their revolution in their annual orbits, together with their gradations of light and heat, are also in proportion to their solar proximity. From the Sun, the Planets, with their surrounding moons, derive heat and light; and when this is intercepted by any planet, or its satellite, an eclipse or darkness ensues. In what periods those tremendous celestial bodies, named Comets, revolve round the Sun, is not yet exactly adjusted.

      One of the seven planets, the Earth, this small domain of restless mortals, and to which all our future observations shall be directed, is distant from the Sun 95,173,000 miles. In shape, it has more resemblance to a turnip than to a globe. Its diameter is 7,970 miles: its circumference 360 degrees; which amounts to 24,840 English miles. Geographers divide the globe of our planet into two equal parts, or hemispheres, the northern and southern, by an imaginary girdle, or ring, named the Equator. Two other imaginary girdles surrounding the earth, and distant from the equator on each side 23½ degrees, north and south latitude, are named the Tropicks of Cancer and Capricorn; comprehending between them the torrid zone. From these tropical circles the zones, called Temperate, extend on each side 43 degrees: and at their extreme boundaries, we reach the polar circles 23½ degrees distant from each pole. The north and the south poles are in the middle of each hemisphere of the earth; and the distance of each from the equator is 90 degrees.

The earth has several incessant motions: one in which it turns, like a suspended wheel upon its own axis, from west to east, every twenty-four hours, which is the length of its day and night: the second, where it is rolling progressively in its great annual circle, or journey round the Sun: the third, the alternate inclination of its poles towards the sun at different times of the year: the fourth, the small circle which it describes monthly round the common center of gravity, or balance, with its moon. The earth’s diurnal revolution upon its axis, is at the rate of fifteen degrees, or 1,035 miles hourly. But the rapidity with which it is whirled in its annual orbit, is, hourly, 68,243 miles: whereas the swiftness of a ball discharged from a cannon is, in the same time, only 480 miles. Projected through the vacuity of heaven with this amazing velocity, in the space of 365 days, 5 hours, and 49 minutes, the earth completes its annual circle; which is the length of our year. The earth’s rotation every twenty-four hours upon its axis, is the cause of day and night, or of light and darkness. In this successive rotation, one half of its globular surface is always enlightened; the other half being then obscured in nocturnal gloom, except when enlivened by the reflected rays of the moon, or of one of the planets, or by the fainter glimmering of the fixed stars. The alternate spiral inflection and declination of the earth’s poles during its annual journey round the Sun, is the cause of the different lengths of Days and Nights; of the Seasons; of Summer and Winter; of the Equinoxes, and Solstices: and as each pole inclines or recedes, it is summer and winter, alternately, in their respective hemispheres. The effects of this compound terrestrial circumvolution on the animal and vegetable creation, would alone be a magnificent theme for many volumes.

One Moon only is allotted to our earth; from which it is distant 240,000 miles. The moon’s diameter is nearly one fourth less than that of the earth, which it obsequiously accompanies throughout its annual circuit; and round which it makes a perpetual revolution, from west to east, every lunar month. The constant agitation and periodical surges of the ocean, are greatly influenced by the moon, assisted, however, by the centrifugal force of the earth’s motion. It is also ascertained, that in some diseases, the human body is considerably under the lunar influence; and its energy is still more conspicuous at periodical changes, during the month and the year. Many arguments might be suggested to invalidate and overturn the ancient astrological systems, and to prove that the celestial influences upon us are not, in any considerable degree, derived from sources more remote than the solar confines.

      The first Element in pre-eminence and subtility, without which all would be lifeless chaos in our system, is Heat and Light. Cold is a negative quality, and merely a comparative diminution of heat. The middle regions of the earth being repeatedly more exposed to the Sun’s vertical rays, are consequently most heated and scorched. From the equator to the poles, are all the gradations of heat and cold; but for reasons too prolix to enumerate, these gradations are not in exact measurement with the geographical distances from the equator; neither in the same continent, nor in different continents. By the scale of Farenheit’s thermometer, water boils at 212, freezes at 32; and blood-heat, or that of the human body, is about 97. The most intense heat of the tropical regions, as measured by the same thermometer, is frequently many degrees above the human temperature; and the most intense cold of the polar regions, often many degrees below 1 or 0 of the same scale. Neither of these noxious extremes of pestilential heat, nor of deadning blasts from boreal snow, could be long endured by the human species, were their bodies not protected and skreened by fences of nature or of art. Atmospheric heat, equal even to that of the human body, is felt intolerably scorching and suffocating. Every one also knows, by personal experience, that in different latitudes, and in summer and winter, the degrees of heat and cold, the duration, recurrence, and changes, are extremely variable. But within the equatorial limits, these variations are much less conspicuous, both in the thermometer and barometer. From this main spring and soul of animated nature, blessings and bounties are diffused, in thousands of channels, to every order of the creation; and from its extremes and vicissitudes, a multitude of evils and diseases are inflicted upon man.

Between the earth and celestial vacuum is interposed an element, called the Atmosphere, or Air. This invisible elastic fluid is floating equally round our planet, to the distance of at least forty-five miles perpendicular elevation. It has been compared by some philosophers, to packs of wool heaped on each other: that nearest the ground is most dense, compact, and ponderous; and as we ascend, it becomes gradually more rare, light, and cold. The prodigious gravity, or pressure, of this atmospherick column, appears incredible to those who are ignorant of experimental philosophy, and of the air-pump and barometer. Upon a man’s body, of middle stature, its weight is equal to thirty-two or thirty-three thousand pounds: but in rainy and variable weather, and especially on the summit of high mountains, there is a diminution in its pressure of many thousand pounds. This great mass of air, as well as the waters of the ocean and of rivers, is in constant agitation; sometimes gliding in gentle calms; sometimes, with wild uproar, raging in storms and hurricanes, and dispersed in a variety of currents, over different parts of the earth and ocean in Winds, constant, periodical, variable, and irregular. Without the concurrent support of air, animal and vegetable life would soon be annihilated. On them great and sensible effects are produced by the atmosphere and winds: by the air’s noxious impregnation, stagnation, want of elasticity, heat, cold, moisture, dryness; by the points from whence winds blow, their constancy, irregularity, recurrence, velocity.

The earth is the cistern, and one principal fountain of another still grosser element. From the Sun’s heat, and from the successive streams of air and winds, a prodigious evaporation is carried on from СКАЧАТЬ