lanes, is a bridge cabin in which is located the machinery for controlling the draw, and at each end of the span are traffic gates capable of being swung across the roadway on the land approach to the bridge. The east traffic gates are operated by the bridge captain and the west gates by the bridge operator through control from the bridge cabin. The two employees constitute the bridge crew. The bridge is equipped with a red ball, 18 inches in diameter, which may be run up and lowered from the bridge operator's cabin, and a city ordinance requires that vessels may not attempt to pass a drawbridge unless the red ball is up.
The bridge was also equipped with an air whistle to warn approaching vessels if, forany reason, the bridge would not be opened in time for safe passage. This whistle was not blown. It is conceded that the bridge operator, though hearing the preliminary whistle, had left his station in the bridge cabin, from which the mechanism for opening and closing the draw is operated, and did not return to his post until after the accident. The bridge captain knew that the operator was not at his post, but there was no arrangement for him to give the warning signal. He testified: "I did not know how to blow the whistle and no one ever showed me." When the steamer was about 800 feet above the bridge, its captain heard the traffic bell which signaled the stoppage of pedestrian and automobile traffic on