174 



SCIENTIFIC RECREATIONS. 



ears, as shown in fig. 1 74 ; we then slightly swing the spoon until we make 

 it touch the edge of the table ; the transmission of sound is in consequence 

 so intense that we are ready to believe we are listening to the double 

 diapason of an organ. This experiment explains perfectly the transmission 

 "of spoken words by means of the string of a telephone, another contrivance 

 which any one may make for himself without any trouble whatever. Two 

 round pieces of cardboard are fitted to two cylinders of tin-plate, as large round 

 as a lamp-glass, and four-and-a-half inches in length. If the two rounds of 

 cardboard are connected by a long string of sixteen to eighteen yards, we 

 can transmit sounds from one end to the other of this long cord ; the 



Fig. 174. Conductibility of sound by solid bodies. 



speaker pronouncing the words into the first cylinder, and the listener 

 placing his ear against the other. It is easy to demonstrate that sound takes 

 a certain time to pass from one point to another. When one sees in the 

 distance a carpenter driving in a stake, we find that the sound produced by 

 the blow of the hammer against the wood only reaches the ear a few seconds 

 after the contact of the two objects. We see the flash at the firing of a 

 gun, before hearing the sound of the report of course on the condition that 

 we are at a fairly considerable distance, as already remarked upon. 



We can show the production of the Gamut by cutting little pieces of 

 wood of different sizes, which one throws on to a table; the sounds produced 

 vary according to the size of the different pieces. The same effect may be 



