The chemical elements, which actually exist in nature as simple bodies, are probably but few. Most of the gases are in all probability compounds of some ethereal ultimate principles; and with the advance of science we may fairly hope to discover the means of reducing some of them to a yet more simple state.
Curious relations, which can be traced through certain bodies, lead us to believe that they may be only modified conditions of one element. Flint and charcoal do not at first appear allied; but carbon in some of its states approaches very near to the condition of silicon, the metallic base of flint. When we remember the differences which are evident in three forms of one body—coke, graphite, and diamond—the dissimilitude between flint, a quartz crystal, and carbon, will cease to be a strong objection to the speculation.
Phosphorus, sulphur, and selenium, have many properties in common. Iodine, bromine, chlorine, and fluorine, appear to belong to the same group. Iron and nickel, and cobalt, have a close relation. Silver and lead are usually combined, and exhibit a strong relationship. Gold, platinum, and the rarer metals, have so many properties in common, that they may form a separate group from all the others.
Indeed, a philosophical examination of the elements now supposed to constitute the material world, enables us to divide them into about six well-defined groups. Wide differences exist within these groups; but still we find a sufficient number of common properties to warrant our classing them in one family.
The dream of the alchemists, in the vain endeavour to realise which they exhausted their lives and dissipated their wealth, had its foundation in a natural truth. The transmutation of one form of matter into another may be beyond the power of man, but it is certainly continually taking place in the laboratory of nature, under the directing law of the great Creator of this beautiful earth.
The speculations of men, through all ages, have leaned towards this idea, as is shown by the theory of the four elements,—Air, Fire, Earth, and Water,—of the ancients, the three,—Salt, Sulphur, and Mercury,—of the alchemists, and the refined speculations of Newton and Boscovich on the ultimate constitution of matter. All experimental inquiry points towards a similar conclusion. It is true we have no direct evidence of any elementary atom actually undergoing a change of state; but when we regard the variations produced by electrical influence, the changes of state which arise from the power of heat, and the physical alterations produced by light, it will be difficult to come to any other conclusion than that the particles of matter known to us as ultimate are capable of change, and consequently must be far removed from positively simple bodies, since the real elementary atom, possessing fixed properties, cannot be supposed capable of undergoing any transmutation. Allotropism could not occur in any absolutely simple body.
It will now be evident that in all chemical phenomena we have the combined exercise of the great physical forces, and evidences of some powers which are, as yet, shrouded in the mystery of our ignorance. The formation of minerals within the clefts of the rocks, the decomposition of metallic lodes, the germination of seeds, the growth of the plant, the development of its fruit and its ultimate decay, the secret processes of animal life, assimilation, digestion, and respiration, and all the changes of external form, which take place around us, are the result of the exercise of that principle which we call chemical.
By chemical action plants take from the atmosphere the elements of their growth; these they yield to animals, and from these they are again returned to the air. The viewless atmosphere is gradually formed into an organized being, the lordly tree upon whose branches the fowls of the air have their homes, and the human animal, exalted by being charged with a spiritual soul: yet the tree and the man alike are gradually resolved again into thin air. The changes of the mineral world are of an analogous character; but we cannot trace them so clearly in all their phenomena.
The planet on which we live began its course charged with a fixed quantity of physical force, and this has remained constant to the present moment, and will do so to the end of time. By influences external to this earth the balance of these forces is continually disturbed; and in the effort to restore the equilibrium, we have the production of all the varied forms of matter, and the manifestation of each particular physical principle or power. As motion and attraction, balanced against each other, maintain the earth in her elliptical orbit, so the opposition of forces determines the existence of the amorphous rock, the light-refracting crystal, the fixed and flowering plant, and the locomotive animal.
An eternal round of chemical action is displayed in nature. Life and death are but two phases of its influences. Growth and decay are equally the result of its power.