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.