NAVIGATION. 133 



whistles which had previously been in use at 

 their lighthouses ; and in a series of investigations 

 on the transmission of sound, under the auspices 

 of the English Trinity House, with a siren lent 

 for the purpose by the United States Lighthouse 

 Board, Professor Tyndall arrived at the same 

 conclusion, and found that often, and especially 

 in the more difficult circumstances, the siren 

 surpasses a signal gun in audibility at a distance. 

 There being, at all events, no doubt of its constant 

 superiority over fog-horns and steam whistles, it 

 seems that it ought immediately to be substituted 

 for them in our navy as means for communicating 

 intelligence, and giving orders from ship to ship 

 in a fog. Introduced for use in fogs, it will pro- 

 bably soon, in clear weather, supplant flags by 

 day and lamps by night, for much of the ordinary 

 telegraphic work between ships of war when at 

 sea. One thing stands out most clear from 

 the evidence produced at the recent court-martial 

 regarding the loss of the Vanguard, and that is 

 that great improvement in this respect is urgently 

 needed. Short and long blasts of the siren 



