120 SUBMARINE SIGNALING AND A PROPOSED 



longitudinal vibration by a hand-driven silk wheel moistened with alcohol, the wire 

 being fastened to the iron hull of a small tug, he was able to read signals 2.8 kilo- 

 meters distant. It is interesting to note in this connection that during the siege of 

 Paris in 1871, the French endeavored to communicate by means of a submerged 

 bell in the Seine but were unable to reach 2 kilometers, from which failure the 

 French physicist Lucas concluded that submarine signals were incapable of trans- 

 mission in rivers. Fig. 5, Plate 46, shows the wire as used in the experiments on 

 the Danube. 



The secret of the extraordinary eflficiency of this system lies in the fact that the 

 vibrations used are longitudinal and the stresses molecular. Unlike a plucked violin 

 string, where the pitch depends on the tension, the pitch in longitudinal vibrations 

 is independent of its tension. As friction is always rythmic the exciter throws the 

 wire into intense longitudinal oscillations, and a clear and absolutely uniform 

 musical note is generated in the water. In order to produce a note of 1,000 vibra- 

 tions per second most suitable for microphones, the wire is cut for one-half a wave- 

 length. As the velocity of sound in steel is about 16,000 feet per second, the wire 

 would be one two-thousandth, or about 8 feet in length, and this would generate a 

 sound wave of about 4.7 feet in the water. Wide limits are practicable, and the 

 most efficient wave-length for submarine signals has not yet been determined. 



An efficient submarine signal system is urgently needed for submarines. Our 

 navy had begun to equip with a submarine bell mounted outside the hull, but the 

 dull "click" of a submarine bell did not lend itself to Morse signals. The clear 

 musical note emitted by the Berger apparatus possessed the valuable quality of an 

 easily distinguishable and sustained note, capable of being sent in dots and dashes 

 of the Morse code. The sound has the qualities of the aerial wireless, and it has 

 therefore been called submarine wireless. 



On August 4, 1912, U. S. Submarine E-i was equipped with the identical wire 

 and exciter used in the Danube experiments, and readable signals were trans- 

 mitted and received over a range of 2 knots off Newport, R. I. The same month 

 another experiment was made by the submarines off Provincetown, using the same 

 silk wheel exciter but substituting a wire of 4 millimeters diameter. Messages 

 were received over a range of 4 miles. 



The results of these tests were so encouraging that a larger apparatus was 

 next constructed, using a half horse-power motor to drive the exciter, and the size 

 of the wire was increased to a flat steel strip having a thickness of -^ inch and a 

 width of ^ inch. 



The apparatus is shown in Fig. 6, Plate 47. A commercial type of Morse key 

 not shown operated the magnetic clutch shown on the motor shaft, and by this 

 means Morse signals were generated by starting and stopping the felt wheel which 

 in operation presses the steel ribbon, not shown in the figure. A test of this set in- 

 stalled on the Submarine E-i was made in December, 191 2, off Hampton Roads. 

 Readable messages were sent and received for several hours at various distances 

 while the E-i was under way and submerged. A range of 7.8 knots was obtained 



