SOUND-SIGNALS AT SEA. 97 



TMs method is also used to some extent by steamers on the 

 great rivers. And it is practiced on the Great Lakes to some 

 extent, notably at a certain bluff jutting out into Lake Superior. 

 Passing steamers, knowing themselves to be in the vicinity, when 

 befogged, feel out these bluffs by sounding their fog-signals 

 until they get back an echo ; then they use the bluffs as a new 

 point of departure. 



In this connection I may say that in the summer of 1886 I 

 experimented in making echoes while on a lighthouse steamer 

 on Long Island Sound, and found I could get a good echo by 

 sounding the whistle of my steamer when passing a sailing-vessel, 

 preferably a schooner, on a parallel course. Wave-sounds strik- 

 ing her sails at right angles to her course, gave a good echo at 

 five hundred yards or less, and the sound of the echo was more 

 or less good within that distance, in proportion to the angle made 

 by the courses of the two vessels when their courses were not par- 

 allel. When off Block Island cliffs, which overhang somewhat, I 

 got a good echo when about a mile distant. Hence I infer that 

 the position of suspected dangers of certain kinds can be deter- 

 mined by the production of echoes under specified circumstances. 



Recent papers state that Mr. H. B. Cox, an electrician whose 

 laboratory is at Fernbank, some ten miles from Cincinnati, has 

 invented a trumpet to be used for telephoning at sea, on which 

 he has been at work for some months. The invention is the out- 

 growth of his discovery of the great distance an echoed or rever- 

 berated sound will carry, and the discovery that speaking-trum- 

 pets, if made to give the same fundamental note, would vibrate 

 and produce the phenomenon known in acoustics as *' sympathy." 



With this trumpet conversation in an ordinary tone of voice 

 was carried on between parties four and a quarter miles apart. 

 People a mile away, conversing in an ordinary tone, could be 

 distinctly heard, and in two instances they were told the nature 

 of their conversation, and admitted that such had taken place. 

 The whistle of a train was traced beyond Fernbank to Lawrence- 

 burg, Ind. It was found that the instrument has a well-defined 

 range of twenty-six miles ; that is, a loud sound like a locomo- 

 tive-whistle, or the rumbling of a train, can be distinctly heard 

 at a distance of thirteen miles in every direction. Conversation 

 was readily carried on between two gentlemen on high hills on 

 opposite sides of the Ohio River distant about four and a half 

 miles apart. Tests made on the water, of various kinds, showed 

 that the trumpet was even more available than on land. 



It is generally understood that Mr. Edison, who has invented 

 so many good things, is now at work, and has made promising 

 yoL. XXXIII. — Y 



