36 BULLETIN OF THE 



ward, go aloft ; and that, when approaching it from the leeward, 

 the nearer he can get to the surface of the water the sooner he will 

 hear the sound. 



It also appears that there are some things the mariner should not 

 do. 



He should place no negative dependence on the fog-signal ; that 

 is, he should not assume that he is out of hearing distance because 

 he fails to hear its sound. 



He should not assume that, because he hears a fog-signal faintly, 

 he is at a great distance from it. 



Neither should he assume that he is near to it because he hears 

 the sound plainly. 



He should not assume that he has reached a given point on his 

 course because he hears the fog-signal at the same intensity that he 

 did when formerly at that point. 



Neither should he assume that he has not reached this point 

 because he fails to hear the fog-signal as loudly as before, or because 

 he does not hear it at all. 



He should not assume that the fog-signal has ceased sounding be- 

 cause he fails to hear it even when within easy earshot. 



He should not assume that the aberrations of audibility which 

 pertain to any one fog-signal pertain to any other fog-signal. 



He should not expect to hear a fog-signal as well when the up- 

 per and lower currents of air run in different directions ; that is 

 when his upper sails fill and his lower sails flap; nor when his 

 lower sails fill and his upper sails flap. 



He should not expect to hear the fog-signal so well when between 

 him and it is a swiftly flowing stream, especially when the tide 

 and wind run in opposite directions. 



He should not expect to hear it well during a time of electric 

 disturbance. 



He should not expect to hear a fog-signal well when the sound 

 must reach him over land, as over a point or an island. 



