Signalling and Safety at Sea, 1& 



on a chart: a zig-zag red line connecting the determinations 

 of distance by the bell and a similar blue line those by the 

 whistle. Both these lines cross and recross the true course,, 

 which appears as a straight black line. The true course was 

 found by range-finder and compass. 



The experiment is highly instructive. The outstanding 

 features are (a) the fact that both bell and whistle when 

 heard suffice to determine the distance with fair accuracy :: 

 (b) the failure of the aerial sounds when the ' Washington } 

 was quite close to the lightship, the bell being still audible 

 in spite of the unfavourable presentation : (c) the distance 

 of hearing the bell being cut down to 2 miles owing to» 

 sternward presentation : (d) its audibility on favourable 

 bearings over a wide angle to 8J miles, and (e) its audibility 

 at 5J miles when the approach of the sound was sternward 

 at 19° with the course : (/) the maximum carriage of tho 

 aerial sounds — 7 J miles — is exceeded by that of the submarine 

 bell. The ultimate limit of audibility of the latter was not 

 reached. 



The general conclusion must be that with favourable 

 presentation the submarine sound affords a more reliable 

 signal than aerial sound. The causes of its failure can be 

 foretold and are not capricious. It is certain that if at any 

 time the 'Washington' had been swung into a more favourable 

 course the sounds would again have been heard. On the 

 other hand the loss of aerial signals is capricious and cannot 

 be anticipated, and swinging the ship must fail to recover 

 them. 



That the U.S. Government were satisfied with the results. 

 of this experiment is shown by the recent establishment 

 on Fire Island Lightship, off New York Harbour, of a 

 synchronized signal station, involving the emission of sub- 

 marine bell-sonnds and wireless dots. 



Synchronous signalling is, therefore, in practical use. 

 This first installation professes to be in a sense experimental,. 

 " although this station has proved accurate on test." Ship 

 captains are asked to report their experience to the Hydro- 

 graphic Department. The British Board of Trade has 

 recently issued to mariners the requisite notice and descrip- 

 tive particulars. " The apparatus will be in operation during 

 fog, mist, rain or falling snow. The range of this apparatus 

 is limited to the receiving range of the submarine bell 

 receiving equipment employed on shipboard, and in all 

 practical cases this is within six or seven miles. The sub- 

 marine bell strikes six strokes, pause, then eight strokes 

 once every 38 seconds." The series of radio signals begins, 



