A ball shot from a cannon, receives its first impulse from the powder; but it is borne thro the air by the aid of a principle inherent in itself, which power is finally overcome by the density of the atmosphere which impedes its progress, and the law of gravitation finally attracts it to the earth. These contending principles may be known by observing the curved line in which the ball moves from the cannon's mouth to the spot where it rests. But if there is no power in the ball, why does not the ball of cork discharged from the same gun with the same momentum, travel to the same distance, at the same rate? The action commences in both cases with the same projectile force, the same exterior means are employed, but the results are widely different. The cause of this difference must be sought for in the comparative power of each substance to continue its own movements.
Every boy who has played at ball has observed these principles. He throws his ball, which, if not counteracted, will continue in a straight line, ad infinitum—without end. But the air impedes its progress, and gravitation brings it to the ground. When he throws it against a hard substance, its velocity is not only overcome, but it is sent back with great force. But if he takes a ball of wax, of snow, or any strong adhesive substance, it will not bound. How shall we account to him for this difference? He did the same with both balls. The impetus given the one was as great as the other, and the resistance of the intervening substance was as great in one case as the other; and yet, one bounds and rebounds, while the other sticks fast as a friend, to the first object it meets. The cause of this difference is to be sought for in the different capabilities of the respective balls. One possesses a strong elastic and repelling power; in the other, the attraction of cohesion is predominant.
Take another example. Let two substances of equal size and form, the one made of lead, the other of cork, be put upon the surface of a cistern of water. The external circumstances are the same, but the effects are widely different—one sinks, the other floats. We must look for the cause of this difference, not in the opposite qualities of surrounding matter, but in the things themselves. If you add to the cork another quality possessed by the lead, and give it the same form, size, and weight, it will as readily sink to the bottom. But this last property is possessed in different degrees by the two bodies, and hence, while the one floats upon the water, the other displaces its particles and sinks to the bottom. You may take another substance; say the mountain ebony, which is heavier than water, but lighter than lead, and immerse it in the water; it will not sink with the rapidity of lead, because its inherent power is not so strong.
Take still another case. Let two balls, suspended on strings, be equally, or, to use the technical term, positively electrified. Bring them within a certain distance, and they will repel each other. Let the electric fluid be extracted from one, and the other will attract it. Before, they were as enemies; now they embrace as friends. The magnet furnishes the most striking proof in favor of the theory we are laboring to establish. Let one of sufficient power be let down within the proper distance, it will overcome the power of gravitation, and attract the heavy steel to itself. What is the cause of this wonderful fact? Who can account for it? Who can trace out the hidden cause; the "primum mobile" of the Ptolmaic philosophy—the secret spring of motion? But who will dare deny that such effects do exist, and that they are produced by an efficient cause? Or who will descend into the still more dark and perplexing mazes of neuter verb grammars, and deny that matter has such a power to act?
These instances will suffice to show you what we mean when we say, every thing acts according to the ability God has given it to act. I might go into a more minute examination of the properties of matter, affinity, hardness, weight, size, color, form, mobility, &c., which even old grammars will allow it to possess; but I shall leave that work for you to perform at your leisure.
Whoever has any doubts remaining in reference to the abilities of all things to produce, continue, or prevent motion, will do well to consult the prince of philosophers, Sir Isaac Newton, who, after Gallileo, has treated largely upon the laws of motion. He asserts as a fact, full in illustration of the principles I am laboring to establish, that in ascending a hill, the trace rope pulls the horse back as much as he draws that forward, only the horse overcomes the resistance of the load, and moves it up the hill. On the old systems, no power would be requisite to move the load, for it could oppose no resistance to the horse; and the small child could move it with as much ease as the strong team.
Who has not an acquaintance sufficiently extensive to know these things? I can not believe there is a person present, who does not fully comprehend my meaning, and discover the correctness of the ground I have assumed. And it should be borne in mind, that no collection or arrangement of words can be composed into a sentence, which do not obtain their meaning from a connection of things as they exist and operate in the material and intellectual world, and that it is not in the power of man to frame a sentence, to think or speak, but in conformity with these general and exceptionless laws.
This important consideration meets us at every advancing step, as if to admonish us to abandon the vain project of seeking a knowledge of language without an acquaintance with the great principles on which it depends. To look for the leading rules of speech in set forms of expression, or in the capricious customs of any nation, however learned, is as futile as to attempt to gain a knowledge of the world by shutting ourselves up in a room, and looking at paintings and drawings which may be furnished by those who know as little of it as we do. How fallacious would be the attempt, how much worse than time thrown away, for the parent to shut up his child in a lonely room, and undertake to impress upon its mind a knowledge of man, beasts, birds, fish, insects, rivers, mountains, fields, flowers, houses, cities, &c., with no other aid than a few miserable pictures, unlike the reality, and in many respects contradictory to each other. And yet that would be adopting a course very similar to the one long employed as the only means of acquiring a knowledge of language; limited to a set of arbitrary, false, and contradictory rules, which the brightest geniuses could never understand, nor the most erudite employ in the expression of ideas. The grammars, it was thought, must be studied to acquire the use of language, and yet they were forgotten before such knowledge was put in practice.
A simple remark on the principles of relative action, and we will pass to the consideration of agents and objects, or the more immediate causes and effects of action.