The ancients believed the metals to be compounds, and this view may be correct. They are now considered to be simple substances, not because they are known to be undecomposable, but because they have never yet been decomposed. Fifty years ago upwards of a dozen bodies were regarded as elements which are now known to be compounds of metals with oxygen.
Who can tell what another period of fifty years may do for alchemy? It is quite possible that at the end of that time the sixty-three so-called simple bodies may be found to be mere modifications of three or four elements, or perhaps of one primordial substance.
These considerations lead us to reflect on the curious transformations which occur in the properties of certain elementary bodies, and which must be regarded as instances of transmutation. Now, a difference in the properties of two compounds having the same composition, may arise from a difference in the arrangement of their ultimate particles; but how is it with the different forms assumed by a simple body? A mass of phosphorus is supposed to be an aggregate of similar atoms, yet this and many other substances of a simple nature, are liable to strange variations of condition which we are as yet unable to explain.
The element carbon exists in many different states. This irregular lump of charcoal, this light powder called lamp-black, and this hard semi--
