Fig. 9
"Now connect this miniature telephone switchboard lamp with the magneto ([Fig. 9]) and turn the crank fast. The lamp lights up to full brilliancy and you notice that the light is steady, although it is made by an alternating current passing through the filament in one direction, stopping entirely, and then passing in the opposite direction. The filament has no time to cool off, provided you turn fast enough, but try turning a little slower and you will notice the flickering of the lamp."
III
THE AMMETER
Fig. 10
At the last meeting of the Science Club so many questions were asked, which the demonstrators could not answer, that a programme committee, to whom such questions might be referred thereafter, was appointed. It was made the duty of this committee to assign to various members the task of searching for satisfactory answers, and when the material was ready to be reported to the club, the programme committee determined the time and order of presentation. I found that I had been made an honorary member of this committee and that it was expected that I should steer the committee. I told them that I accepted this appointment with the understanding that the fellow who steers is always the smallest man in the crew, and if they would do all the work I would enjoy the honorary title of cockswain. Secretly, however, I appreciated that this was in effect adding several courses to my already rather heavy programme. I must, under the régime, direct a large number of inexperienced students in library research, in laboratory research, and in the art of giving demonstrations with apparatus and experiments to audiences.
The most urgent questions, as also those which were next in the natural order, concerned the ammeter. I told the committee to make that the subject of the next meeting and to send to my laboratory on a certain day the person or persons whom they might appoint to report upon it.