Signalling and Safety at Sea. 31 



of an unfamiliar instrument, may create the impression that 

 the proposed system of averting collision is one involving" 

 rather complicated operations ; and these too at a time Avhen 

 simplicity and clearness of procedure are above all desirable. 

 In order to show how unfounded this impression is we shall 

 now follow the necessary steps as they would be taken 

 on an adequately equipped ship in order to ascertain if there 

 was risk of collision with another vessel. We may continue 

 to call our own vessel A and the other vessel B. 



The scene is once more in the North Atlantic. The 

 weather is thick and night falling'. Vision is restricted to a 

 couple of ship's lengths. The Officer of the Watch has at 

 hand a Predictor which is already set to the course and speed 

 of his own ship. 



The operator in charge of the wireless room has started 

 into action a clockwork contact-maker which automatically 

 sends out, periodically, the wireless fog signals required by 

 (future) Board of Trade rules. 



Presently he hears the characteristic radio signals of 

 another vessel. He calls the other ship ; communicates his 

 own course and speed and learns hers in exchange. These 

 he reports at once to the Officer of the Watch who adjusts 

 the other limb of the Predictor accordingly, and reads 

 forthwith the danger rate and danger bearing proper to the 

 courses and speeds of the two vessels. 



Meanwhile the wireless operator has signalled to the other 

 ship asking for signals whereby the bearings may be 

 determined. He makes an estimate of the bearing; informs 

 the other ship u You bear NNE." ; and then reports this 

 bearing to the Bridge. 



The Officer of the Watch is now able to say right off that 

 the signals must be continued. For on comparing this 

 bearing with the danger bearing he perceives that they are 

 indistinguishable. On board the other ship the same decision 

 is come to. 



Our ship now signals to B, by code, " Bearing dangerous : 

 prepare to receive distance signals/' Then when B acknow- 

 ledges this the wireless operator on our ship sets in operation 

 the automatic emission of synchronous signals. These 

 continue to be emitted till B reports " Distance 5 miles." 



When this is reported to the Bridge the Officer marks the 

 arm c of his Predictor at the reading 5 miles, and makes in 

 his own mind an estimate of the minutes still to run before 

 collision can occur. He finds there are 12 minutes. He may 

 note the time or start a stop-watch. 



