The Operation and Use of the Apparatus 



hard the echo would also be sharp and short, but as the 

 clouds only vary slightly in density from the surrounding 

 air, the sound is much modified and softened that is, par- 

 taking in no small degree of the nature of the reflecting body. 

 Clouds are of all densities and are at various distances. The 

 primary vibrations produced by the lightning are echoed and 

 re-echoed between the clouds and the earth, producing a very 

 complicated series of sounds of widely varying degrees of 

 intensity. Thunder is a reflection that reveals the character 

 of the object in our vicinity. Would not a blind man with 

 good ears and a knowledge of the laws of sound as relates 

 to thunder be able to judge something of the nature of his 

 surroundings by the character of the thunder ? In the system 

 of Zadig described by Voltaire, we find what a lot of infor- 

 mation one is able to obtain from very slender data. The 

 same idea is elaborated by Sir Conan Doyle in his " Sherlock 

 Holmes." In my apparatus, we have to examine certain little 

 zigzag lines on a strip of paper ; the relative size of the zig- 

 zags, their position on the paper, and their number, can be 



read and understood without the use of anything approaching 







the skill of Zadig or Sherlock Holmes. In order to bring 

 this subject within the grasp of all, let us suppose a case. 



We will imagine that all ships of any considerable size 

 crossing the Atlantic are provided with my apparatus. We 

 embark on one of these ships at New York at 4 o'clock in 

 the afternoon, and a few hours later we are well out on 

 the Atlantic in a moderate sea way, and adjust our receiver 

 so that the small bell sounds about every ten seconds, due 

 to the noise of the wind and waves. We try our recording 

 instrument, and find that it only produces a wavy line, quite 



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