CURRENT TOPICS.

In Davy Jones’ Locker.-(General Elechic Review, Vol. 40, No. 6.) When Captain John D. Craig descends this summer to the wreck of the Lusitania to film the scheduled salvage operations, his equipment will include a battery of the most powerful lamps ever designed for deep sea work. The new lamps, developed by engineers of the General Electric Co., are built to withstand a water pressure of 500 lb. per sq. in., more than three times the pressure encountered around the hull of the vessel, submerged in 312 feet of water off the Irish Coast, where the pressure is 150 lb. per sq. in. Each lamp has a light output of 137,500 lumens. A set of twelve of them will be mounted on a special submarine stage, to floodlight the scene. The intense heat at which the lamps operate would cause them to fail in a few minutes if burned in the open air. Due to the cooling action of the water, however, they will function for 25 hrs. The bulbs, made of special, hard ultra-violet transmitting glass to provide the best possible photographic light, are filled with a mixture of nitrogen and argon, and fitted with special rubber insulation to insure perfect waterproofing.

R. H. 0.

Solar Energy and Its Use for Heating Water in California.-The practical utilization of the vast amount of solar energy is not easy. In the past there have been various attempts to do this which were more or less successful. At the present time, however, direct use of solar energy is being made by several thousand solar water heaters in California, according to F. A. Brooks in Bulletin 602 of the University of California, College of Agriculture. Successful use depends, of course on the number of sunshine days. Many different types of solar water heaters have been developed, primarily based on the nature of the hot water demand.

R. H. 0.

Power Production from Tropical Vegetable Waste.-_VER SOEHNER begins a series of articles on this subject in Engineering, Vol. CXLIII, No. 3723, in which there is given an account of what has been designed and constructed in the way of suction gas plants. Among the materials used in such plants are included cotton capsules and cotton seed coats, palm nuts, cocoa, brazil nuts, olive husks,

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