We cannot, by any comparison with the labours of the most skilful human artisan, convey an idea of the exquisite perfection of planetary mechanics, even so far as they have been discovered by the labours of science; and we must admit that our insight into the vast machinery has been very limited. All we know is the fact that this planet moves in a certain order, and at a fixed rate, and that the speed is of itself sufficient to rend the hardest rocks; yet the delicate down which rests so lightly upon the flower is undisturbed. It is, therefore, evident that matter is endued with powers, by which mass is bound to mass, and atom to atom; these powers are not the results of any of the motions which we have examined, but, acting in antagonism to them, they sustain our globe in its present form. Are there other motions to which these powers can be referred? We know of none. That absolute rest may not exist among the particles of matter is probable. Electrical action, chemical power, crystalline aggregation, the expansive force of heat, and many other known agencies, are in constant operation to prevent it. It must, however, be remembered, that each and every atom constituting a mass may be so suspended between the balanced forces, that it may be regarded as relatively at rest. Theory imagines Motion as producing Force--a body is moved, and its mere mechanical change of place is regarded as generating heat; and hence the refinements of modern science have advanced to the conclusion that motion and heat are convertible. Admitting that the material atoms of which this world is formed are never in a state of quiescence, yet we cannot suppose any gross ponderable particle as capable of moving itself; but once set in motion, it may become the secondary cause of motion in other particles.[10] The difficulties of the case would appear to have been as follows:--Are heat, light, electricity, &c., material bodies? If they are material bodies--and heat, for example, is the cause of motion--must not the calorific matter move itself--or if it be not self-moving, by what is it moved? If heat is material, and the primary cause of motion, then matter must have an innate power of moving; it can convert itself into active force, or be at once a cause and an effect, which can scarcely be regarded as a logical deduction. We move a particle of matter, and heat is manifested; the force being continued, light, electricity, and chemical action result; all, as appears from a limited view of the phenomena, arising out of the mechanical force applied to the particle first moved.[11] This mechanical force, it must be remembered, is external to the body moved, and is, in all probability, set up by the movement of a muscle, acted upon by nerves, under the influence of a will.