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54 Propellers Prove Durakle (Continued from Page 23) United States, and one visit to Chile by way of the Straits of Magellan. At none of the periodical inspections have any traces of corrosion or other failure of the monel metal propellers been found. Although the vessel has made frequent full speed runs ag- gregating over 38500 nautical miles at 20 to 22 knots, there was discovered no trace of surface imperfection from erosion, according to the reports re- MARINE REVIEW Although this vessel has not been very active as compared to the mile- age made by the transatlantic liners or some of our own modern cruisers of the navy, the conditions met by the unprotected propellers while the ship was at anchor are more serious from the standpoint of a corrosion test than if the vessel had been engaged in more steaming at moderate speeds. One of the accompanying illustra- tions showing in end-on view all three propellers indicates that the tips of the blades of the center wheel have PORT WING PROPELLER ON THE ARGENTINE BATTLESHIP RIVADAVIA IN DRY DOCK IN BOSTON—THOUGH IN SERVICE 14 YEARS THE ORIGINAL MACHIN- ING TOOL MARKS ON THE FACE OF THE LOWER BLADE ARE STILL TO BE SEEN ceived of the inspection of these pro- pellers when the vessel was in dry dock. It seems that none of the condi- tions of the service of this vessel, in tropical sea water, ice, or brackish riv- ers, has made any attack upon the face of the monel metal blades, and the rate of corrosion on the customary plates provided for protection against galvanic effect is about one-half. of that ordinarily experienced. In fact one of the accompanying views quite clearly shows the original tool marks on the face of one of the blades. Remembrance of the famous tele- phone cases of over forty years ago is recalled in a_ decision recently handed down by Judge Lowell of the Sounding Patent Basic been cut off, for a distance of some 6 inches from the tips. This pro- peller was so trimmed when the ves- sel was in dry dock in Boston during last winter in order to provide a greater clearance from the stern frame in the hope of eliminating a certain characteristic vibration which seemed to originate under the coun- ter. It had been suggsted that this vibration might be caused by water thrown against the hull. It is not known, at the time of writing this, if the results were favorable. Federal district court of the United States sustaining the Fessenden pat- ent No. 1,217,585 in a suit brought by the Submarine Signal Corp., Boston, September, 1926 against the General Radio Co. Judge Lowell, in sustaining the con- tention that Professor Fessenden was the first inventor of an_ electrical method of depth sounding now em- ployed in the submarine Fathometer, said in part, “Fessenden discovered a new method. The telephone cases are ample authority for the support of his claims which were very skillfully Crawn, with the fifth claim of one of Bell’s patents as a model.” The submarine Fathometer, which is based on Fessenden’s discovery, sends sound impulses periodically to the bottom of the sea where they are reflected upward and then excite an electric ‘sound receiver. The latter, by means of an electrical mechanism and a beam of light, indicates con- tinuously, on a calibrated dial, the depth of water a vessel is in. Professor Fessenden’s discovery of this new method of depth sounding is linked in its history with the sinking of the TiTanic. It was this appalling disaster which led Professor Fessen- Jen to experiment with his oscillator for the purpose of detecting the pres- ence and proximity of icebergs by means of an echo. Original Oscillator Tests In 1914, Professor Fessenden made tests on the revenue cutter MIAMI while the latter was on its usual ice patrol off the Grand banks. In these tests Professor Fessenden found that the oscillator could be used not only to detect the presence and nearness of icebergs, but also, to determine the depth of water that the revenue cut- ter was in, by measuring the elapsed time between the sound of the os- cillator and the return of the echo. The subsequent development of Professor Fessenden’s invention, the submarine Fathometer, has resulted in a new and efficient method of tak- ing soundings. Various types of ves- sels, from submarines to ocean liners, are already equipped with the device. The present decision is of interest in that it gives to Professor Fessen- den proper credit for his successful pioneer work in determining the depth of water by electrical means. ie Self-Unloading Freighter Ordered by Bradley Ever’ since’ the self - unloading steamer T. W. ROBINSON was com- pleted at the Lorain, O., yard of the American Shipbuilding Co., over a year ago, there has been under con- sideration the construction of a similar vessel. The experience with the ROBINSON indicates that the bold step taken of fitting her with turbo-elec-