As the flame is lighted for only one-tenth of the signal period, it will be seen that the saving of gas amounts to 90 per cent., as compared with the light which is burning constantly. Accordingly, the gas charge will last ten times as long with the flashing apparatus; consequently, the accumulator need have only one-tenth of the capacity of that for a similar beacon which burns constantly. The economy really is not quite 90 per cent., as a certain volume of gas is consumed by the pilot flame, which ignites the charge of gas issuing from the flasher burner. This, however, is an insignificant item, inasmuch as the quantity of gas burned by the pilot light does not exceed one-third of a cubic foot per twenty-four hours. Not only has this highly ingenious system been adapted to varying types of buoys, similar in design and range of action to those described in connection with the Willson apparatus, wherein the light may be left unattended for as long as twelve months, according to the capacity of the accumulator, but it has also been applied to “light-boats” and light-vessels. The “light-boat” is a hybrid, being a combination of the buoy and the lightship, and was devised to meet special conditions. Thus, the “Gerholmen” light-boat stationed in the mouth of a Swedish river, where the current runs exceedingly strongly, resembles a small boat with a water-tight deck. From the centre of this rises a steel tripod, at the top of which the lantern is placed. The gas accumulators are stored within the hull, and are of sufficient capacity to maintain the light for a round twelvemonth without attention, as the flashing apparatus is incorporated. The Aga light has come to be regarded as one of the greatest developments in lighthouse engineering, and has been adopted extensively throughout the world in connection with either floating or fixed aids to navigation. The United States have decided to adopt the system exclusively henceforth, until a further progressive step is achieved, and several floating lights of this type have been acquired already to guard wild and lonely stretches of the coastline. Here and there attempts have been made to apply electricity to inaccessible lights. The most interesting endeavour in this direction was in connection with the lighting of the Gedney Channel from the open Atlantic to New York harbour. This formerly constituted the only available highway for the big liners, and it is exceedingly tortuous and treacherous--so much so that vessels arriving off Sandy Hook in waning daylight invariably anchored and awaited the dawn before resuming the journey. The great difficulty in connection with Gedney’s Channel was the distance of the main lights on shore, the direct range at one part being over thirteen miles. Consequently the land lights were of little utility to the pilot.