This instance is but a typical example of chemical decomposition in general, and may occur in thousands of different ways in different chemicals, and producing not only chemical transformation, but the manifestation in many cases of heat, and light, and electricity, etc. I will next speak of electricity and chemical affinity conjointly. The electrical spark will produce heat, light, chemical change, and movement. Faraday showed also that electricity produces magnetism, and magnetism electricity—that indeed you can not produce the one without the other. Again, electricity will set in motion chemical affinity or decomposition, and conversely chemical change will produce heat, light, electricity, motion, etc. To show this, place pieces of zinc and copper in an acid—that is, make a voltaic battery. The acid attracts the metal and sets up chemical action, and the result is that this chemical action by producing a change of state, sets free electricity, which being conducted by “the poles” or wires of the battery can there be made manifest in the following different ways: Bring the poles together and heat, light, motion, etc., will be produced as witnessed in the dazzling electric light. Or, to produce chemical change only, plunge the wires constituting “the poles” of the battery into water, and wonderful to say the molecules of water will have such motion imparted to them that they will be broken up into their constituent gases; and what is most marvelous, the oxygen will always be given off at one pole and the hydrogen at the other. This is electrolysis or electro-chemical decomposition. Numbers of compounds in solution may have the molecular states of their atoms broken up thus, by the voltaic current, and curious to say of the atoms so dissevered, as above noted, those composing a given element will always be evolved by the same pole—the positive pole or the negative pole as the case may be. Some elements, that is to say, always appearing at the positive pole and others always at the negative. Lastly I will say a few words specially as to motion. We saw how the motion of striking the lucifer match produced chemical change, and light, and heat. We have seen also that chemical change—that is, the movement and change of place of the infinitely small atoms of matter—could be produced by heat, and light, and electricity; and that chemical change could also itself interchangeably produce all these.