The Poetry of Science; or, Studies of the Physical Phenomena of Nature

by Robert Hunt

The golden glories of sunset,—when, “like a dying dolphin,” heaven puts on the most gorgeous hues, which are continually changing,—depend entirely upon the quantity of watery vapour which is mixed with air, and its state of condensation. It has been observed, that steam at night, issuing into the atmosphere under a pressure of twenty or thirty pounds to the square inch, transmits and reflects orange-red light. This we may, therefore, conclude to be the property of such a condition of mixed vapour and air, as prevails when the rising or the setting sun is shedding over the eastern or the western horizon the glory of its coloured rays.[227]

Thus science points out to us the important uses of the air. We learn that life and combustion are entirely dependent on it, and that it is made the means for securing greater constancy in the climates of the earth than could otherwise be obtained. The facts already dwelt upon are sufficient to convince every thinking mind that the beautiful system of order which is displayed in the composition of the atmosphere, in which the all-exciting element, oxygen, is subdued to a tranquil state by another element, nitrogen, (which, we shall have presently to show, is itself, under certain conditions, one of the most energetic agents with which we are acquainted,) indicates a supreme power, omniscient in the adaptation of things to an especial end. Oxygen and nitrogen are here mixed for the benefit of man; man unites them by the aid of powers with which he is gifted, and the consequences are of a fatal kind. The principles which the great Chemist of Nature renders mild are transformed into sources of evil by the chemist of art.

Beyond all this, the atmosphere produces effects on light which add infinitely to the beauty of the world. Were there no atmosphere, we should only see those objects upon which the sun’s rays directly fell, or from which they were reflected. A ray falling through a small hole into a dark room, illuminating one object, which reflects some light upon another, is an apt illustration of the effect of light upon the earth, if it existed without its enveloping atmosphere. By the dispersive powers of this medium, sunlight is converted into daylight; and instead of unbearable, parallel rays illuminating brilliantly, and scorching up with heat those parts upon which they directly fall, leaving all other parts in the darkness of night, we enjoy the blessings of a diffusion of its rays, and experience the beauties of soft shades and slowly-deepening shadows. Without an atmosphere, the sun of the morning would burst upon us with unbearable brilliancy, and leave us suddenly, at the close of day, at once in utter darkness. With an atmosphere we have the twilight with all its tempered loveliness,—a “time for poets made.”

In chemical character, atmospheric air is composed of twenty-one volumes of oxygen, and seventy-nine volumes of nitrogen: or one hundred grains of air consist of 23·1 grains of the former, and 76·9 grains of the latter. Whether the air is taken from the greatest depths or the most exalted heights to which man has ever reached, an invariable proportion of the gases is maintained. The air of Chimborazo, of the arid plains of Egypt, of the pestilential delta of the Niger, or even of the infected atmosphere of an hospital, all give the same proportions of these two gases as we find existing on the healthful hills of Devonshire, or in the air of the city of London. This constancy in constitution leads to the supposition that the oxygen and nitrogen are chemically combined; but many eminent philosophers have contended that they are merely mechanically mixed; and they have shown that some peculiar properties prevail amongst gaseous bodies, which very fully explain the equal admixture of two gases the specific gravities of which are different. This is particularly exemplified in the case of carbonic acid, of which gas one per cent. can be detected in all regions of the air to which the investigations of man have reached. This gas, although so heavy, is, by the law of diffusion, mixed with great uniformity throughout the mass.[228] Every exhalation from the earth, of course, passes into the air; but these are generally either so light that they are carried into the upper regions, and there perform their parts in the meteorological phenomena, or they are otherwise very readily absorbed by water or growing plants, and thus is the atmosphere preserved in a state of purity for the uses of animals. Again, the quantity of oxygen contained in the air, and its very peculiar character, ensures the oxidation of all the volatile organic matters which are constantly passing off,—as the odoriferous principles of plants, the miasmata of swamps, and the products of animal putrefaction; these are rapidly converted into water, carbonic acid, or nitric acid, and quickly enter into new and harmless combinations. The elements of contagion we are unacquainted with; but since the attention of inquirers has been of late directed to this important and delicate subject, some light may possibly be thrown upon it before long.

Nothing, shows more strikingly the admirable adaptation of all things for their intended uses than the atmosphere. In it we find the source of life and health; and chemistry teaches us, most indisputably, that it is composed of certain proportions of oxygen and nitrogen gases; and experience informs us that it is on the oxygen that we are dependent for all that we enjoy. So beautifully is the atomic or molecular constitution ordered, that it is impossible to produce any change in the air without rendering it injurious to the vegetable and animal economy. It might be thought, from the well-known exhilirating character of oxygen gas, that, if a larger quantity existed in the atmosphere than that which we find there, the enjoyments of life would be of a more exciting kind; but the consequences of any increase would be exceedingly injurious; and, by quickening all the processes of life to an unnatural extent, the animal fabric would soon decay: excited into fever, it would be destroyed by its own fires. Chemistry has made us acquainted with six other compounds of oxygen and nitrogen, neither of them fitted for the purposes of vitality, of which the following are the most remarkable:—

Nitrous oxide, or the, so called, laughing gas, which contains two volumes of nitrogen to one of oxygen, would prove more destructive than even pure oxygen, from the delirious intoxication which it produces.

Nitric oxide is composed, according to Davy, of two volumes of nitrogen and two of oxygen. It is of so irritating a nature, that the glottis contracts spasmodically when any attempt is made to breathe it; and the moment it escapes into the air it combines with more oxygen, and forms the deep red fumes of nitrous acid.

Nitrous acid and the peroxide of nitrogen each contains an additional proportion of oxygen, and they are still more destructive to all organization.

Nitric acid contains five volumes of oxygen united to two of nitrogen; and the well-known destructive properties of aqua fortis it is unnecessary to describe.