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December, 1923 MARINE REVIEW 473 ships shows the necessity of increas- ing the ease of steering, especially with a view to affording protection against attacks by submarines. Several rud- ders of the usual design had, there- fore, to be provided, each of *which was hardly substantial enough to stand the considerable pressures correspond- ing to the high speeds. The new scheme will enable a single rudder of excessive dimensions to be provided, which, while being much more eff- cient than a standard rudder, has to comply with much smaller require- ments with regard to the strength of its design. A warship thus equipped obviously possesses superiority in ma- neuvering: The excellent results given by the first rudder of this type induced the Hamburg-American line of Hamburg, to equip the twin-screw motorship OvENWALD of 8000 tons as well as a 9300-ton freight ship now in course of building, with Flettner rudders. Trial _ trips made with the former have given as much satisfaction as in the case of the Fricmo. e wus, ie aa Ane ?, ‘Sun Valve Acts in Place a Lighthouse Keeper —~ HOW NEW RUDDER IS FITTED, THE VIEW SHOWING CLEARLY METHOD OF OPERATION : feature of the new rudder, which has been brought out in actual practice, is the remarkablessteadiness of the steer- ing effort’ exerted on the ship. In fact, apart fromthe practically instan- tanéous setting of the rudder, such fluctuations as are, otherwise produced by variations in flow are here entirely done away with, the rudder being perfectly free from any rigid connec- tion with the vessel and, accordingly, responding instantaneously, like a spring, to any deflecting force, in or- der immediately to return into the po- sition assigned to it by the deflector. It is interesting to note how in bad weather, in a rough sea, etc., the index of the main rudder gage continually moves to and fro slightly, while the ship keeps the steadiness of her course unaltered and steering is reduced to a minimum. The fact that the main rudder axis does not transmit any twisting effects obviously adds to the safety of the scheme. The absence of any rudder engine, of course, means a reduction in first cost, operating ex- penses, repairs, superintendence and upkeep. The development of modern war- In the accompanying photograph models. of beacons and lighthouses using v3 ” Ane: aS the “Aga” type of lights. are shown. . Lights of this type are now in use along the American coasts and at the Panama canal. They have the magic quality of lighting up automati- cally at nightfall or in the case of a heavy fog, and of extinguishing themselves at the return of daylight. These lights operate by means of acetylene gas stored in tanks, and the automatic control is effected by the use of an interesting sun valve in- vented by Gustaf Dalen of “Sweden. This type of light is manufactured in America by the Gasaccumulator Co., Newark, N. J. The sun valve is actuated by light and is not influenced by changes in temperature. Its operation is based on the well known physical law that ab- sorbed light is transformed into heat. Four metal rods protected by a strong glass cylinder form the basis of the system. The central rod is coated with lamp black which gives it the property of absorbing light, while the three rods surrounding it are polished, thus reflecting the light. Consequently all four rods expand the same amount under the influence of heat, but only the central rod expands under the influence of light. The expansion or lengthening of the central rod caused by heat due to absorbed light serves to operate a valve which controls the \