We will now connect with our laboratory current a 32-candle-power lamp, an ammeter, and a wattmeter, all in series, Fig. 18, and in parallel with these a volt meter. This last instrument indicates the electric pressure. Its mechanism will be examined later. The volt meter indicates 110 volts and the ammeter shows that one ampere is passing. The filament in the lamp resists the passage of the current. It gets quite hot and gives forth as much light as thirty-two candles. Its resistance is just such that 110 volts of pressure send one ampere through it. We will now take the reading of the wattmeter, note the time and read it again later. One hour later its index showed that 110 watt hours of electrical energy had been converted into light and heat. This at the usual rate, costs 1.1 cents, one cent per hundred watt hours or ten cents per thousand watt hours, called a kilowatt hour. The more common 16-candle-power lamp costs about half a cent an hour to operate. It requires one horse-power to keep fourteen of them burning. [Illustration: Photograph by Helen W. Cooke. Wattmeter] I will now take you to see the wattmeter which measures all the electric energy used in this building. You note down its reading and the date and the next time you come we will read it again and thus find out how much electricity has been used for electric lights, for electric ventilating fans, for electric elevators, for electric ovens, and electric irons in the school of household arts, for electric motors to run lathes and other machines in the school of technical arts, for electric experiments in my laboratories and lecture room, for electric vacuum cleaners and, lastly, for pumping the pipe organ in chapel. I saw by the boys' faces as they departed what would be the next question that they would bring to me. Knowing, however, that the hour was up, they were too polite to press it then. V THE ELECTRIC MOTOR In a few days I received a telephone message, asking if I could appoint an hour to meet the programme committee in my laboratory. I must confess that my pleasure in these meetings had increased so much that I was quite ready to slight other duties, if need be, to engage in them. Moreover, since my business was education it was not difficult for me to regard these meetings in the light of a duty quite as important as my regular class instruction--perhaps more effective. At any rate the boys and I managed to get together. May God forgive the man who essays to teach boys, but does not love to be with them.