But probably the most complete and useful type of Willson acetylene gas beacon is that in which the Courtenay whistling device is incorporated, so that in thick weather audible warning of the danger may be extended. In this instance the floating chamber which supports the superstructure carrying the light and also the generator tube, is fitted with two further tubes which project from the base like huge legs. These tubes are open at the bottom, but are closed at the top except for a connection with a valve-casing, which is fitted with a ball-valve, and upon which a powerful whistle is bolted. Now, if the buoy is lowered and anchored in absolutely still water, the water will rise to the same level within the tubes as it is outside; but when the buoy is lifted upon the crest of a wave, the level of the water falls, so that the air space within the tubes is increased. Air enters this augmented space through the ball-check inlet valve in the valve-casing. When the beacon falls, naturally the water endeavours to maintain its level within the tubes, and therefore the air which was admitted into the space becomes compressed, to be expelled through the only possible vent--the whistle--thereby producing a very powerful blast. Thirty of these combined light and whistling buoys have been strung along the rugged Nova Scotia coast, and have proved highly popular, that outside Halifax harbour being known colloquially among seafarers as the “Outer Automatic.” Another acetylene system, but working upon a better principle, has been perfected in Sweden, and, indeed, now has been adopted universally, owing to its many excellent features. This is the “Aga” light, which is the invention of Mr. Gustaf Dalén,[C] and which has been brought to a high stage of commercial success by the Gas Accumulator Company of Stockholm. I have pointed out the one objection to the Willson acetylene automatic light--namely, its uselessness when the surrounding water becomes frozen. While this drawback does not affect its sphere of utility to a noticeable degree in Canadian waters, it acts somewhat adversely in other seas where similar conditions prevail, but where the navigable channels are kept open by ice-breakers, such as, for instance, in the Baltic Sea. Mr. Dalén recognized this weak point in any system wherein contact with water is responsible for the generation of the gas, and accordingly sought for a superior method. Fortunately, the perfection of a new means of handling acetylene, by French inventors, offered the complete solution of the problem in a practical way. The principle of this lies in the use of dissolved acetylene, which is perfectly safe from explosion, and can be handled with the greatest facility. The gas can be stored in cylinders similar to those used for containing oxygen and hydrogen under pressure, gases which are easier to transport than carbide of calcium, and, what is far more important, climatic conditions do not exercise the slightest influence