132 DISCUSSION ON TWO PRECEDING PAPERS. 



changing their bearing ; and second, not to have to change his speed and course in a fog unless 

 absolutely necessary. 



My proposed method fulfils all these conditions. 



Most of the collisions in a fog occur after vessels sight each other and while both are 

 maneuvering to avoid collision, and the method proposed by Mr. Millet for obtaining direc- 

 tion by submarine signals would tend to produce exactly this situation. Even if we assume 

 that you determined the bearing of the other vessel exactly, so long as you had no knowledge 

 of her distance there might still be danger of collision. 



If we compare the submarine system alone with the wireless system alone for obtaining 

 bearings in a fog, the wireless appears clearly superior, as the radio-goniometer does not re- 

 quire any change of course to ascertain the bearing. Both depend for accuracy upon the rel- 

 ative degree of intensity of the sounds, and are therefore affected by errors both of the ob- 

 server and of the instrument. 



As the intensity curve of sound is sinuous, the lack of definite fix hardly supplies the 

 wants of the practical navigator, while a reasonably accurate knowledge of the distance 

 would exactly meet his needs. 



The submarine signal will owe its imique value in fog navigation to the fact that in 

 combination with wireless it will make possible accurate knowledge of the distance separa- 

 ting vessels, and make it possible to know whether the bearing is changing, with ample dis- 

 tance remaining to change course if necessary. 



No other methods will accomplish this result. 



The Chairman : — I am advised that just before the close of the morning session there 

 is to be an interesting moving-picture film to be shown in connection with Mr. Tawresey's 

 paper, which was read yesterday, on the launching of the Oklahoma. 



We will now have paper No. 12, "The Behavior of Riveted Joints under Stresses," by 

 Mr. James E. Howard. 



Mr. Howard's paper was presented. 



