MAGNETIC TELEGRAPH. 19 



the scientific labor done by Professor Henry at 

 Princeton, during those years when his chief duties 

 were instruction, and when he had only a portion 

 of his time in which to work for mankind and for 

 reputation ; and I must be content with a passing 

 glance at a part of it. 



Among those wires which were strung across 

 the campus in 1835, was one used for a mag- 

 netic telegraph between the professor's home and 

 his laboratory in the Philosophic Hall; and that 

 telegraph line was the first in the world in which 

 the galvanic circuit was completed through the 

 earth one end of the single wire-circuit ter- 

 minating in the well at the house, and the other 

 in the earth at the Hall. Steinheil, in Munich, 

 in 1837, worked his electric telegraph in the 

 same way by a single line wire, using the earth 

 as part of the circuit, over much longer distances; 

 but it was first done in this campus. 



Nearly a century earlier our great countryman, 

 Franklin, had drawn from a surcharged thunder- 

 cloud, upon the string of a kite, in a pouring shower 

 of rain, the lightning of heaven, and had demon- 

 strated its identity with the puny spark of an 

 electrical machine; and with that capital experi- 

 ment his fame is more closely associated than with 

 any other of the great truths he discovered. In 

 these grounds that experiment was amplified, and 

 still further results obtained, by the man for 



