The l^hree Secretaries 129 



searches, all of which are described in Doctor T-aylor's well- 

 known discourse. 1 There he prosecuted his later studies 

 upon induction. He developed his apparatus for the combi- 

 nation of circuits, the principle of which underlies the various 

 forms and uses of the relay magnet, and the receiving magnet 

 and local battery, since employed in the telegraph. He car- 

 ried on his classical investigations upon successive orders of 

 induction. 2 He found that a second induced current could 

 induce a third, and the third a fourth, and so on indefinitely ; 

 that a current of intensity could produce one of quantity, and 

 the converse ; and that these currents could be induced at a 

 distance. He obtained an induced current in one room from a 

 primary current in the next room. From two wires stretched 

 perpendicularly several hundred feet apart, and finally con- 

 necting the tin roof of his house with his study, he mag- 

 netized needles by induction from a thundercloud eight miles 

 away. 



The discovery of the oscillatory character of the discharge 

 from the Leyden jar one of his most important contribu- 

 tions to science followed in 1842. He ascertained that in 

 the discharge of a jar an equilibrium is not instantaneously 

 effected by the spark, but is attained only after several oscil- 

 lations of the flow ; a fact which was not only in itself signifi- 

 cant, but led to important advances in theory. 3 As Doctor 

 Oliver Lodge has shown, the explanations offered by him in 

 connection with these early experiments were almost pro- 

 phetic of the great generalizations subsequently made by 

 Clerk Maxwell and others, but which in the state of electrical 



1 Taylor, William B., " The Scientific Work 3 See Barker, George F., " Physics," New 

 of Joseph Henry." Bulletin of the Philo- York, 1892, page 613; Lodge, Oliver J., 

 sophical Society of Washington, 1878, Vol- " Modern Views of Electricity," London, 

 ume II, page 230. "Memorial of Joseph 1889, page 369; Taylor, W. B., "Memorial 

 Henry," 1880, pages 205-425. of Joseph Henry," page 255 ; Houston, 



2 Transactions American Philosophical So- Edwin J., " Electricity a Hundred Years Ago 

 ciety, 1838, Volume vi, page 303. and To-day," New York, 1894, page 6l. 



