I have now shown you that in order to produce light we must, by some means or other, raise the temperature of a body. But the high temperature that we have to deal with is not that produced by the combination of the oxygen of the air and carbon, and other bodies such as I have shown you, but it is produced by the aid of the electric current. In all these cases the result of the combustion you have seen has been to remove oxygen from the air, but now I want to show you how a body can be raised to a high state of temperature without combustion of any kind. In front of me I have a fine platinum wire. In my hand I hold a wire that is in connection with a battery upstairs, the other wire in connection with the battery is attached to the far end of the fine platinum wire; now, when I make contact with the near end of the platinum wire, you observe that the wire is raised to redness, its temperature is high, and as I reduce the length of the platinum wire it gets brighter and brighter, the amount of electricity passing through it is greater and greater, and presently the wire is fused. I should have pointed out that as the quantity of heat generated in a wire increases, so does the color of the light. When heat is applied to a body, that body is first warmed, then it gets gradually hotter and hotter, until it becomes red hot, and the first color that appears is always red. The temperature is further raised, and the body assumes the color of orange, then at a little higher temperature it appears yellow, and so the different colors of the rainbow are perceived according to the different temperatures to which the body tested with is raised. Now, I want to show you the most intense form in which heat can be produced on this earth. There is no hotter object that we can obtain than that of the electric arc. I will try and produce this arc. You observe that when I bring these two pieces of carbon together, a current of electricity passes between them, and the passage of the current of electricity between them creates such an intense temperature that a brilliant white light, as you see, is produced. Incandescent particles of carbon pass between the two points, forming a sort of bridge or arch, which is called the electric arc. But the temperature of this arc is, as I said before, the highest temperature that we can produce; it has been measured, and is found to be 8,500° Fahr. That is a temperature that can hardly be conceived; the melting point of iron is only about 1,200° Fahr.; the melting point of platinum, which is one of the most refractory metals we have, is about 3,000° Fahr.; but here in the arc we have the intense temperature that nothing can withstand, equal to 8,500° Fahr. The color is really due to the combustion that takes place between the materials forming the arc. I have just used two pieces of carbon, but I will now try other materials--copper, iron, and zinc. You will see a difference in the