50 PROFESSOR HENRY AND THE 



ranged by combinations of the successive move- 

 ments of the vanes, or afterwards of the needle of 

 the Gauss and Weber telegraph he hears letter 

 after letter tapped out, and the message is under- 

 stood. 



Now, that apparatus has nothing about it 

 more than was in Henry's Albany telegraph of 

 1831; nor could it operate if it omitted any one of 

 the inventions, either singly or together, which 

 were then for the first time combined. It depends 

 entirely upon the discoveries made by Henry before 

 1831; and it could not have existed in the world 

 earlier than those discoveries, by the use of any 

 means then known to man ; nor since by any 

 other means than those discovered by Henry. 



Henry used a bell as a sounder; they now use 

 a metal bar and a sounding box. Henry reversed 

 the battery current, whereby no spring is needed 

 to withdraw the armature for the purpose of 

 vibrating it; and that is the common practice in 

 English and German telegraphs. Here they 

 generally merely interrupt the circuit, and the 

 armature is withdrawn from the magnet by a 

 spring; although Henry's device is also used here 

 largely, and is essential to the quadruplex instru- 

 ments.* 



If, however, the telegraph line is a long one it 

 may be a thousand miles or more then you will 



* See Appendix, Note X. 



