Of course, at times gas is liable to be generated more rapidly than it can be consumed. What happens? The apparatus is not provided with facilities to receive the surplus gas. Being unable to escape upwards through the generator tube, it collects at the bottom, and as the pressure increases it gradually forces the water away from the carbide, so that generation ceases, and is not resumed until the surplus gas has been absorbed, when the water once more is able to come into contact with the carbide. Thus it will be seen that the gas generation is controlled automatically, and that it is almost impossible for the gas pressure within the plant to reach a disruptive degree, owing to the fact that when it exceeds a certain limit it has a free vent from the bottom of the device, where the water normally is permitted to enter to carry out its designed purpose. This invention has been utilized for a wide variety of purposes, from the lighting of harbours, navigable channels, rivers, bays, and so forth, to that of exposed coasts. The automatic beacon, properly so called, has a tower, which brings the focal plane to an elevation varying between 50 and 100 feet, this tower being built of lattice steelwork attached to the top half of the buoy, with a day mark surrounding the lantern gallery, access to which is secured by an iron ladder. This type of light carries a sufficient storage of carbide in a single charge to keep the light burning continuously for about forty weeks. In this instance the only modification from that already described is that the water for the production of the gas is admitted into the top instead of to the bottom of the generator. When an excess of gas occurs, the pressure thereof drives the water away from the carbide until the surplus has been consumed. Another type, somewhat smaller, carrying a charge sufficient for nearly six months, has proved highly successful as a coastal light, some thirty beacons of this class being stationed along the shore of British Columbia. The only trouble experienced therewith in these waters has been due to frost, which, solidifying the water around the buoy, has interrupted the designed functions.