the smith's shop, and you see him put the handle of a poker on to the stem, and by a little management and the application of heat he makes them one. You have no doubt seen him put the iron into the fire and sprinkle a little sand upon it. He does not know the philosophy he calls into play when he sprinkles a little sand over the oxide of iron, but he has a fine philosophy there, or practises it, when he gets his welding. I can shew you here this beautiful circumstance of the sticking together of the particles up to the fullest possible intensity of their combination. If you were to go into the workshops of Mr. Matthey, and see them hammering and welding away, you would see the value of the experiment I am about to shew you. I have here some platinum-wire. This is a metal which resists the action of acids, resists oxidation by heat, and change of any sort; and which, therefore, I may heat in the atmosphere without any flux. I bend the wire so as to make the ends cross: these I make hot by means of the blowpipe, and then, by giving them a tap with a hammer, I shall make them into one piece. Now that the pieces are united, I
