At the meeting of the Chemical club last evening Mr. Crawley read a very interesting paper on the principal theories of the construction of matter. The first thing in regard to the construction of matter of which we have any account is what may be called the "substantia" theory which maintains that all matter had for its basis a certain principle, a substance, and the various forms in which matter exists are the results of different influences brought to bear upon the primary substance. This theory was superseded by the four element theories of the school of Aristotle which taught that all matter was the result of the combination of tire, water, earth and air This theory held during the Middle Ages and was the inspiration of the Alchemists who thought that, since all the metals were composed of these four elements and no others, it would be possible to convert the baser metals into the precious ones by a simple change. The decomposition of water by Lavasier, of course, broke up this theory, since one of the supposed elements was compound, and not an element in itself. Very soon after this we have the Daultorian theory of atoms which is our modern chemical theory.