With such strong encouragement, is it any wonder that the three young men continued their operations vigorously?  Not one of them scarcely wanted to stop long enough to eat and sleep, _a la_ Edison; and as it was now summer vacation time, Paul and Bob were able to be with John all day long in the old exhibition building.  Neighboring boys and even older people hung around the open doors to watch operations, but the builders were careful not to let them get close enough to gain any ideas which might be harmful to their interests.