Steam was used to sound the whistle, located on top of the building, and also to power a small piston engine beside the boiler. This engine regulated the timing of the whistle blasts and pumped more water into the boiler. Every twenty-four seconds a rotating cam in the engine alternately triggered blasts of four and eight seconds. Mariners could check the latest issue of the Light List to identify the station from the characteristic of either the light or the fog signal. Early view of fog signal building.
Steam whistle is immediately to left of large smokestack.
The whistle was sometimes more important in aiding mariners than the light. In dense fog or heavy rain East Brother's powerful light was virtually useless. The ten-inch whistle, on the other hand, could often be heard from ten or twelve miles away. Through the years many a ship captain groped his way across the misty bay waters guided only by the regular blasts of East Brother's fog signal. It took many years' experience to learn to navigate in this way.