A steam vessel when towing shall, instead of the signal prescribed above, at intervals of not more than one minute, sound three blasts in succession, namely, one prolonged blast followed by two short blasts. A vessel towed may give this signal and she shall not give any other.
All rafts or other water craft, not herein provided for, navigating by hand power, horse-power, or by the current of the river, shall sound a blast of the fog horn, or equivalent signal, at intervals of not more than one minute.
Steam Vessel Signals.
One blast—I am directing my course to starboard.
Two blasts—I am directing my course to port.
Three blasts—I am going astern.
The vessel that blows first has the right of way.
Passing through narrow channels a vessel must keep to that bank of the fairway which is on her starboard hand.