BIOGEAPIIICAL MEMOIR OF JOSEPH HENRY. 161 



f^lectro-inagnet into tlie condition necessary to its nse in telegPciphy, and 

 also to point out its application to the telegrapli, and to illustrate this 

 by constructing a working telegraph, and, had 1 taken out a patent for 

 my labors at that time, Mr. Morse could have had no ground on which 

 to found his claim for a patent for Lis invention. To Mr. Morse, how- 

 ever, great credit is due for his alphabet, and for his i^erseverance in 

 bringing the telegraph into practical use. 



II. My next investigation, after being settled at Princeton, was in re- 

 lation to electro-dynamic induction. Mr. Faraday had discovered that 

 when a current of galvanic electricity was passed through a wire from 

 a battery, a current in an opposite direction was induced in a wire ar- 

 ranged parallel to this conductor. I discovered that an induction of a 

 similar kind took place in the i^rimary conducting wire itself, so that a 

 current which, in its passage through a short wire conductor, would 

 neither produce sparks nor shocks, would, if the wu-e were sufficiently 

 long, produce both these phenomena. The effect was most strildngly 

 exhibited when the conductor was a tlat ribbon, covered with silk, rolled 

 into the form of a helix. With this, brilliant deflagrations and other 

 electrical effects of high intensity were produced by means of a current 

 from a battery of low intensity, such as that of a single element. 



III. A series of investigations was afterward made, which resulted in 

 producing inductive currents of different orders, having different direc- 

 tions, made up of waves alternately in opposite directions. It was also 

 discovered that a plate of metal of any kind, introduced between two 

 conductors, neutralized this induction, and this effect was afterward 

 found to result from a current in the plate itself. It was afterward 

 shown that a current of quantity was capable of producing a current 

 of intensity, and, vice versa, a ciu'rent of intensity would produce one 

 of quantity. 



IV. Another series of investigations, of a parallel character, was made 

 in regard to ordinary or frictional electricity. In the course of these it 

 was shown that electro-dynamic inductive action of ordinary electricity 

 was of a peculiar character, and that effects could be produced by it at 

 a remarkable distance. For example, if a shock were sent through a 

 wire on the outside of a building, electrical effects could be exhibited in 

 a parallel wire within the building. As another illustration of this, it 

 may be mentioned that when a discharge of a battery of several Ley- 

 den jars was sent through the wire before mentioned, stretched acrosvS 

 the campus in front of Nassau Hall, an inductive effect was produced 

 in a parallel wire, the ends of which terminated in the plates of metal 

 in the ground in the back cami)us, at a distance of several hundred feet 

 from the primary current, the l3uilding of xsTassau Hall intervening. The 

 effect produced consisted in the magnetization of steel needles. 



In this series of investigations, the fact was discovered that the in- 

 duced current, as indicated by the needles, api)eared to change its di- 

 rection with the distance of the two wires, and other conditions of the 

 experiment, the cause of which for a long time baffled inquiry, but was 

 finally satisfactorily explained by the discovery that the discharge of 

 electricity from a Leyden jar is of an oscillatory character, a principal 

 discharge taking place in one direction, and immediately afterward a re- 

 bound in the opposite, and so on forward and backward, until the equi- 

 librium is obtained. 



V. The next series of investigations related to atmospheric induction. 



The first of these consisted of experiments with two large kites, the 



lower end of the string of one being attached to the upper surface of a 



second kite, the string of each consisting of a fine wire, the terminal end 



S. Mis. 59 11 



