Signalling and Safety at Sea. 17 



oscillator travels to the bottom of the sea, conies back by 

 reflexion, and acting on the oscillator generates a current in 

 it. This will be heard in the telephone receiver if the brush 

 connected to the telephone is in contact with the segment 

 just at the instant when the reflected sound impulse reaches 

 the ship. The setting of the telephone brush will, therefore, 

 determine the depth. In a depth of 8 fathoms beneath the 

 oscillator the time for the sound to travel to the bottom and 

 back will be about the one-fortieth of a second. The echo, 

 according to the results of a trial made from a U.S. Revenue 

 Cutter, may be heard in the ship without the use of the 

 receiver. A stop-watch used to determine the interval 

 between the start and return of the sound afforded a good 

 approximation to the depth. 



Experimenting from the same vessel, the distance of an 

 iceberg 450 feet long and 130 feet high was determined by 

 echo from the submerged part of the berg at various distances 

 from one-hair mile to two and one-half miles. The echoes 

 were not only heard in the oscillator receiver, but in the 

 officers' wardroom and elsewhere in the ship. The distances 

 agreed with those determined by the range-finder. The 

 prosecution of the experiments was hindered by rough 

 weather, the oscillator not being permanently installed but 

 lowered overboard. The echoes were loud at 2J miles. It is 

 stated that as regards the intensity of this underwater echo, 

 it made no difference whether the face of the berg was 

 presented to the ship or otherwise. It must be remembered 

 that the immersed volume of the berg was some ten times as 

 bulky as that presented to view. 



Marvellous as all this undoubtedly is, the purely sensational 

 part of it is surpassed by the achievements of wireless 

 telephony. The wireless telephone can speak in plain words 

 to the sailor, telling him the name of the signal station he is 

 approaching and warning him of his danger if he comes 

 too close. The speaker is a machine, a dead thing, and 

 aether waves carry the energy, translated out of its rightful 

 medium, through miles of wild weather, to the ship labouring 

 far off the coast, and there it is again restored to the medium, 

 whereby it reaches the sailor's cognizance. He listens at a 

 telephone in his cabin or wireless room and hears the words 

 reiterated over and over again by the machine in the light- 

 house. At this latest achievement of Science, we feel inclined 

 to say: k ' Hold ! Enough!" 



The wireless telephone is no very recent achievement. 

 Speech has been transmitted by its means from stations in 



Phil. Mag. S. 6. Vol. 36. No. 211. July 1918. 



