nine o'clock at night
From the final tube two thin wires ran to a long tubular coil . To the left of this coil was a large relay switch , and a rheostat control . `` Turn on the relay , Dad , then slowly rotate the controller to the left . And remember that it is rather powerful ; I know this does n't look like a solar engine , and nine o'clock at night seems a peculiar hour to demonstrate such a thing , but I 'll guarantee results -- probably more than you expect . '' Dr. Arcot stepped up to the controls and closed the switch . The lights dimmed a bit , but immediately brightened again , and from the other end of the room came a low , steady hum as the big transformer took up the load . `` Well , from the sound of that ten K.W. transformer there , if this engine is very efficient we ought to get a terrific amount of power out of it . ''