128 POPULAR LECTURES AND ADDRESSES. 



and it has besides the great advantage of showing 

 the receivers exactly where to look for the signals 

 when they come, by keeping the signal lamp 

 always in view in the intervals between signals, 

 instead of keeping it eclipsed in the intervals as in 

 Colomb's method. 



(3) Colomb's method of shorts and longs has 

 also been practised, with great success, in fogs by 

 day and by night, with long and short blasts of 

 the steam whistle or fog-horn, instead of long 

 and short flashes of light. 



67. But here again a very great improvement is 

 to be made. Use instead of the distinction between 

 short and long the distinction between sounds of 

 two different pitches, the higher for the " dot," the 

 lower for the "dash." Whether in the steam 

 whistle or the fog-horn a very sharp limitation 

 of the duration of the signal is scarcely attain- 

 able. There is, in fact, an indecision in the 

 beginning and end of the sound, which renders 

 quick and sure Morse signalling by longs and 

 shorts impracticable, and entails a painful slow- 

 ness, and a want of perfect sureness, especially 



