upon it. [C] The humane labours of Mr. Dalén received recognition by the award of the Nobel Peace Prize in 1912. Dissolved acetylene may be stored within the cylinder, or accumulator, as it is called, to a pressure of at least ten atmospheres, and at this pressure it contains 100 times its own volume of acetylene gas. The accumulators may be made of any desired size, this factor being governed by considerations of transport and application, as well as of the consumption of the burner. The perfection of the dissolved acetylene process came as a great boon to the Swedish lighting authorities, inasmuch as they have probably the most difficult stretch of coastline in the world to protect. At the same time, owing to the wild, exposed character of many of the points which demanded lighting, a perfect, economical, and reliable automatic system was in urgent demand. Acetylene was an obvious illuminant, since, while the country is deficient in the essential resources for the preparation of other fuels, carbide of calcium is very cheap, Sweden, in fact, being the largest producer of this commodity. The Swedish Board of Pilotage experimented with acetylene lighting for six or seven years, submitting every known acetylene lighting system to searching practical trials, but failed to be sufficiently convinced on the vital question of reliability. Freezing-up was the most pronounced shortcoming, but when dissolved acetylene appeared as a commercial product this disadvantage was removed completely, and acetylene was adopted. [Illustration: THE “KALKGRUNDET,” SWEDEN’S LATEST AUTOMATIC LIGHTSHIP. The Dalén Flasher is used, and this undoubtedly is the finest vessel of its type in the world.] Yet dissolved acetylene, though completely successful, possessed one drawback. It was expensive as compared with oil-gas. Accordingly, there was great scope for a means of economizing the consumption of the fuel without interfering with its lighting value and efficiency. At the same time a superior flashing system was desired. The methods which were in vogue to this end were satisfactory so far as they went, but they involved a considerable useless consumption of gas. This is where Mr. Gustaf Dalén completed one of his greatest achievements. He perfected a flashing apparatus wherein the gas passes to the burner in intermittent puffs, to be ignited by a small invisible pilot light. The device was tested and proved so successful that it was adopted throughout the service. In Swedish waters to-day there are 127 aids to navigation operating upon this system, of which five are lightships. The success of the invention in the land of its origin attracted other nations to its possibilities. At the present moment over 700 lights, scattered throughout the world, are working upon this principle.