FARMERS' INSTITUTES. 361 



conducted through the mass of the coudnctor aud is not confined to the surface 

 as m the statical condition.* The question tlius arises, Avhatis the path of con- 

 duction in electricity of high tension? 



Some may ask, what does it matter whether conduction is at the surface or 

 through the mass of a conductor? "Wliy not rest satisfied with the fact that a 

 metallic rod will conduct electricity witliout questioning closely the path of con- 

 duction? To these questions I offer two answers : 1st, the forces of nature will 

 still act whether we recognize them or not ; they do not suspend their action 

 because of our ignorance ; gravitation did not wait for Newton to discover its 

 laws before it exerted its marvelous pull, which may hold a world in its safe 

 path or overwhelm the luckless traveler with the thundering avalanche. 2d, 

 the use of a scientific fact may outcrop long after the fact was discovered. The 

 principle announced by Christ, " the truth shall make you free," holds in sci- 

 ence as well as in morals. To know and obey all of nature's laws is the only 

 path of safety ; to know that we may obey is the supreme satisfaction of the 

 human soul. 



In entering upon this investigation I found in the text books only the results, 

 and not the processes by which such results had been reached. As I had no 

 access to the original papers, I was thus thrown upon my own resources for such 

 investigation. Fortunately I had in Prof. Henry's letters an outline of the 

 investigations by which he had reached his results. I therefore took them as 

 the starting point in my investigations, and make them the basis of this essay. 



The experiment of Prof. Henry with a magnetizing spiral inside a gun-barrel 

 is a very striking one, and at first sight it seems conclusive against the doctrine 

 of internal conduction of electricity of high tension. I repeated his experiment 

 and found tlie needle in the internal magnetizing spiral only very feebly mag- 

 netic, while the needle in the external spiral was strongly magnetic. Can these 

 results be explained in any way except by the assumption of surface or exterior 

 conduction? Two objections presented themselves to the inference of exterior 

 conduction from this experiment : 1st, Tlie gun-barrel has a large amount of 

 conducting material compared with that of the contained wire. The experi- 

 ment was varied by substituting a large glass tube coated with tin foil in the 

 place of tlie gun-barrel, so as to make the amount of conducting material, 

 external and internal, more nearly equal; on passing a strong charge of fric- 

 tional electricity through this combination, the needle in the internal spiral 

 was strongly magiietic. The experiment Avas again varied as follows : a piece 

 of inch gas-pipe 2G inches long was substituted for the gun-barrel ; in this a 

 stout jiiece of copper wire (one-sixth inch in diameter), was inserted, the wire 

 being coiled into a magnetizing spiral, and a steel needle being placed in the 

 axis of the spiral ; on passing a charge from a battery of ten two-quart Leyden 

 jars, the needle in the internal spiral became magnetic, but less strongly than 

 that in the spiral in the glass tube coated with tin foil. 



This raised the question whether the electricity Avhich passes by the internal 

 wire expended the whole of its magnetizing influence upon the needle within 

 the spiral, or was a portion expended upon the surrounding iron tube, whether 



*C(mducti(jn.—l\\ aU cases where electricity is in motion, whether it be excited by chemical action 

 as in the voltaic pile, or by friction, as in the common electrical machine, the force is conveyed by 

 the entire thickness of the conductor; the charge is not conllned to the surface, as occurs when 

 the power is stationary and produces effects by induction only. In the case of the voltaic current 

 as well as in the momentary discharge of the Leyden battery, by far the greater proportion of the 

 induction occurs between one transverse section of the conductor and the adjacent sections imme- 

 diately before and behind it; and but a small proportion of the induction, sufficient however to be 

 distinctly manifest, is diverted to surrounding objects.— J/iZ?ej-'s Chemical Physics, pp. 404-6. 



46 



