_Answer._ After the signal to start is given by the conductor, the runner also gives a signal by either ringing the bell or blowing the whistle. The latter should, however, be used, especially at stations, as little as possible, on account of the risk of frightening horses and the shock which it produces on persons who are unaccustomed to hearing it, or are suffering from any nervous disorder. After giving the requisite signal, the runner places the reverse-lever so that the valve will work either in full gear or very near it. He then opens the throttle _slowly_ and _cautiously_ so as to start the train gradually. If the train is a very heavy one, it is best to back the engine so as just to “take up the slack of the train,” that is, to push the cars together so that there will be no space between them and thus compress the car draw-springs. When the cars stand in this way, those at the front end of the train are started one after another, which makes the start easier than it would be if it were necessary to start them all at once. If the throttle is opened too rapidly, the driving-wheels are apt to slip, but with a very heavy train, even with the greatest care, this is liable to occur. If the train can not be started otherwise, the rails must be sanded by opening the valves in the sand-box. As little sand should be used as possible, because the resistance of cars running on sanded rails is greater than on clean rails, and thus the train is more difficult to draw after it reaches the rails to which sand has been applied. Thus the difficulty to be overcome may be increased by the means employed to overcome it. While the train is slowly set in motion the fireman and runner must ascertain by watching whether the whole train moves together, and that none of the couplings are broken in starting, and also whether any signal is given to stop, as is sometimes necessary after the train has started. On leaving the station he should observe whether all the signals indicate that the track is clear and that the switches are set right, and also look out for obstructions on the track. The train should always be run slowly and cautiously until it has passed all the frogs, switches and crossings of the station yard, and not until then and when the runner has seen that everything is in order should he run at full speed. As the engine gains in speed the reverse lever should be thrown back and nearer the centre of the quadrant or sector, so as to cut off “shorter.” QUESTION 477. _After the engine is started, how can it be run most economically?_