As we move around our own sun—in the limited period of 365 days, and round our own axis in 24 hours—we experience transitions from heat to cold, dependent upon our position in regard to that luminary and the laws which regulate the reception and retention of certain physical forces. May we not therefore conclude, without being charged with making any violent deduction, that in the great revolution of our system around the centre of space, we are undergoing gradual changes which are essential to the great scheme of creation, though at present incomprehensible to us?
In our consideration of the influence of time on the structure of the earth as we find it, we discovered that, in ages long past, the vegetation of the tropics existed upon these northern parts of the globe; and geological research has also proved that over the same lands the cold of an arctic winter must have long prevailed—the immense glaciers of that period having left the marks of their movements upon the face of the existing rocks.[268] We know that during 3,000 years no change of temperature has taken place in the European climate. The children of Israel found the date and the vine flourishing in Canaan; and they exist there still. Arago has shown that a trifling alteration of temperature would have destroyed one or the other of these fruit-bearing trees, since the vine will not ripen where the mean temperature of the year is higher than 84°, or the date flourish where it sinks below that degree.
How immense, then, the duration of time since these changes must have taken place! The 432,000 years of Oriental mythology is a period scarcely commensurable with these effects; yet, to the creature of three-score years, that period appears an eternity. The thirty-three millions of geographical miles which our solar system traverses annually, if multiplied by three thousand years, during which we know no change has taken place, give us 99,000,000,000 as the distance passed over in that period. How wide, then, must have been the journey of the system in space to produce the alteration in the physical powers, by which these changes have been effected!
We have an example, and a striking one, of the variations which may be produced in all the physical conditions of a world, in those disturbances of Uranus which led to the discovery of Neptune. For thirty years or more certain perturbations were observed in this distant planet, the discovery of Sir William Herschel, and calculation pointed to some still more remote mass of matter as the cause, which has been verified by its actual discovery. But now Uranus is at rest;—quietly that star progresses in its appointed orbit,—Neptune can no longer, for the present, cause it to move with greater or less rapidity—they are too remote to produce any sensible influence upon each other. Consequently, for thirty years, it is evident, phenomena must have occurred on the surface of Uranus, which can be no longer repeated until these two planets again arrive at the same positions in their respective paths which they have occupied since 1812. These considerations assist us in our attempts to comprehend infinite time and space; but the human mind fails to advance far in the great sublimity.
Through every inch of space we have evidence of the exercise of such forces as we have been considering. Gravitation chains world to world, and holds them all suspended from the mystic centre. Cohesion binds every mass of matter into a sphere, while motion exerts a constant power, which tends to alter the form of the mass. The earth’s form—a flattened spheroid—the rings of Saturn and of Neptune are the consequences of motion in antagonism to cohesion. Heat, radiating from one planet to another, does its work in all, giving variety to matter. Light seeks out every world—each trembling star tells of the mystery of its presence. Where light and heat are, chemical action, as an associated power, must be present; and electricity must do its wondrous duties amongst them all. Modified by peculiar properties of matter, they may not manifest themselves in phenomena like those of our terrestrial nature; but the evidence of light is a sufficient proof of the presence of its kindred elements; and it is difficult to imagine all these powers in action without producing some form of organization. In the rounded pebble which we gather from the sea-shore, in the medusa floating bright with all the beauty of prismatic colour in the sun-lit sea,—in the animal, mighty in his strength, roaming the labyrinthine forests, or, great in intelligence, looking from this to the mysteries of other worlds,—in all created things around us, we see direct evidence of a beautiful adjustment of the balance of forces, and the harmonious arrangement of properties.
One atom is removed from a mass and its character is changed; one force being rendered more active than another, and the body, under its influence, ceases to be the same in condition. The regulation which disposes the arrangements of matter on this earth, must exist through the celestial spaces, and every planet bears the same relation to every other glittering mass in heaven’s o’erarching canopy, as one atom bears to another in the pebble, the medusa, the lion, or the man. An indissoluble bond unites them all, and the grain of sand which lies buried in the depth of one of our primary formations, holds, chained to it by these all-pervading forces, the uncounted worlds which, like luminous sand, are sprinkled by the hand of the Creator through the universe. Thus we advance to a conception of the oneness of creation.
The vigorous mind of that immortal bard who sang “of man’s first disobedience,” never, in the highest rapture, the holiest trance of poetic conception, dreamed of any natural truths so sublime as those which science has revealed to us.
The dependence of all the systems of worlds upon each other, every dust composing each individual globe being “weighed in a balance,” the adjustment of the powers by which every physical condition is ordered, the disposition of matter in the mass of the earth, and the close relation of the kingdoms of nature,—are all revelations of natural truths, exalting the mind to the divine conception of the universe.
There is a remarkable antagonism displayed in the operation of many of these forces. Gravitation and cohesion act in opposition to the repellent influences of caloric. Light and heat are often associated in a very remarkable manner; but they are certainly in their radiant states in antagonism to chemical action, whether produced by the direct agency of actinic force, or through the intermediate excitement of the electrical current.[269] And in relation to chemical force, as manifested in organic combinations, we have the all-powerful operation of life preventing any exercise of its decomposing power.[270] As world is balanced against world in the universe, so in the human fabric, in the vegetable structure, in the crystallized gem, or in the rude rock, force is weighed against force, and the balance hangs in tranquillity. Let but a slight disturbance occasion a vibration of the beam, and electricity shakes the stoutest heart with terror, at the might of its devastating power.[271] Heat melts the hardest rocks, and the earth trembles with volcanic strugglings; and actinic agency, being freed from its chains, speedily spreads decay over the beautiful, and renders the lovely repulsive.
We know matter in an infinite variety of forms, from the most ponderous metal to the lightest gas; and we have it within our power to render the most solid bodies invisible in the condition of vapour. Is it not easy, then, to understand that matter may exist equally attenuated in relation to hydrogen, as that gas itself is, when compared with the metal platinum? A doubt has been raised against this view, from the difficulty of accounting for the passage of the physical elements through solid masses of matter. If we, however, remember that the known gases have the power of transpiration through matter in a remarkable degree,[272] and that the passage of water through a sieve may be prevented by heat, it will be at once apparent that the permeation of any radiant body through fixed solid matter is entirely a question of conditions.