114 RECENT DEVELOPMENTS IN SUBMARINE SIGNALING. 



"I assume that you gentlemen have read the paper sufficiently to know that the appara- 

 tus consists principally of two tanks, one on the starboard side and one on the port side, 

 located well forward of the bluff of the bow, so as to present ears forward of the ship, as our 

 own ears are presented forward. In order to ascertain the direction, as I am speaking to 

 you now, you turn your head more or less in order to get the direction of sound, and what 

 happens is that your face makes a sound shadow receiving surface for the ears, and the 

 same principle is applied in the case of the signaling system on board ship. The starboard 

 tank has a transmitter in it connected by wire to the chart room, or wherever desired, and 

 the port tank also has a similar transmitter. These are carbon transmitters, similar to what 

 you speak through in the ordinary telephone system, and therefore as they receive every- 

 thing that comes to them, practically — if you want to ascertain the direction from which 

 any sound is received — all you have to do is to turn the switch from starboard to larboard, 

 and find out by comparing the sound of the bell on one side with the other. If the ship is 

 directed straight on to the mark the sound will be equally loud on each side. Very fre- 

 quently it has been possible to detect the direction within one-eighth of a point. It is as- 

 sumed, in the case of such a fine distinction, that you must have had a little experience in the 

 use of the apparatus so as to be able to absolutely direct your mind to what you are doing. 

 Unfortunately I have been obliged in many cases, in conducting tests for other governments, 

 to call the attention of the men in the chart house to the fact that it would not be considered 

 fair, if you are out on the bridge making this test, that everybody should talk and smoke 

 and shout and whistle. Very frequently the observers who are appointed to report on these 

 tests with me would not stop their conversation, and therefore it required the apparatus to 

 give a more distinct signal than otherwise would be expected. I think that is all I have to 

 say on the subject, and I shall be glad to answer any questions which may be asked." 



The Chairman: — There is another paper on this same subject. No. 15, "Submarine 

 Signaling and a Proposed Method of Safe Navigation in Fogs," by Commander F. L. Saw- 

 yer, U. S. N. Before we take up the discussion on the paper by Mr. Millet, I will ask Com- 

 mander Sawyer to present his paper. 



Commander Sawyer presented the paper, and in connection with its presentation made 

 the following remarks : — 



Referring to the plates, Figs. A and B, Plates 52 and 53, are presented to illustrate a 

 number of typical cases explanatory of the system. Fig. A shows two vessels "A" and 

 "B" each steaming 15 knots and 5 miles apart when the distance is first measured. Vessel 

 "A" is on course East (90°). Take the first case when vessel "B" is assumed to be steer- 

 ing West 270°, or directly opposite the course of "A." In order to collide, "B" would have 

 to be on the same line representing "A's" course. In that case they would be approaching 

 each other at the combined speed of 15 knots each or 30 knots, one mile every two min- 

 utes. As they are 5 miles apart collision would then occur in ten minutes. Referring to Fig. 

 B this line is shown as the collision line marked 270°, a straight line because the bearing 

 does not change, cutting the time scale at ten minutes. The distance actually measured 

 would in the illustration fall upon the curved line 270° shown in Fig. B and the operator 

 on watch would know at once that the vessels were changing bearing rapidly and no col- 

 lision could occur. Fig. B shows that at the time collision would happen the vessels are 

 actually 3.8 miles apart and separating. 



