SCIENCE IN THE INDUSTRIAL WORLD 



made of a small piece of sapphire with a chisel-shaped 

 edge, while the point used in reproducing the sounds is 

 also made of sapphire with its edges rounded and of a 

 peculiar shape. The shape of this little point is very 

 important, as clear reproductions are largely dependent 

 upon its construction. 



The advantage of the wax cylinders over those made 

 of tin-foil is that they are more permanent and may be 

 duplicated by molding an indefinite number of times. 

 Furthermore they record sounds readily and reproduce 

 them better. 



For reproducing sounds three things are necessary 

 in the shape and arrangement of the indentations in the 

 grooves made by the recorder. It will be recalled that 

 the pitch of any sound depends upon its number of 

 vibrations per second sounds of a high pitch or fre- 

 quency having more vibrations than those of a low 

 pitch. On the cylinder, therefore, a high note is recorded 

 by a certain number of indentations in a given space, 

 while low notes have a correspondingly less number. 

 The number of indentations is quite independent of 

 the loudness of the sound to be reproduced ; this is con- 

 trolled by the depth of the indentations made, a loud 

 sound producing deep indentations while softer sounds 

 are represented by shallow ones. 



The fact that these little indentations will reproduce 

 sounds seems wonderful enough to the ordinary mind, 

 but the real wonder lies in the fact that qualities of 

 sounds are also reproduced in the little grooves the 

 violin, for example, being almost as easily distinguish- 

 able from the French horn as it is in the orchestra itself. 



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