364 



STATE BOAKD OF AGEICULTUKE. 



always leaped from the hall of the intei'ioi' wire. This experiment seems to show 

 that conduction of frictional electricity may be by the interior mass of a con- 

 ductor as ■well as at its surface. 



The experiment was tried to see if this kind of electricity could be withdrawn 

 from the interior of a conductor during its passage. Into the opposite ends of 

 a T gas-coupling gas-pipes were firmly screwed ; one end of tlie gas-pipe Avas 

 securely closed by screwing on a brass cap ; into the third opening of the T 

 coupling a glass tube Avas securely cemented, the glass tube being coA'ered with 

 shellac A'arnish to secure good insulation ; a copper Avire was passed through the 

 glass tube so as to touch the inside of the gas-coupling, and the projecting por- 

 tion of the Avire was coiled into a magnetizing spiral ; the free end of the Avire 

 Avas then twisted with a wire attached to the open end of the gas-pipe. Cut V. 

 exhibits the essential parts of this apparatus. 



When a steel needle Avas placed in the spiral and a Leyden jar discharged 

 through the apparatus from -j- to — , the needle AA'as found to be magnetic, thus 

 shoAA^ng that frictional electricity may be withdrawn from the interior of a con- 

 ductor during the passage of a charge of such electricity. A critical friend 

 objected that the electricity Avas still Avithdrawn from a surface, although it was 

 an interior surface. To remoA'C this objection a cylinder of lead Avas cast, con- 

 ducting wires being inserted in each end of the lead cylinder ; a deep hole Avas 

 drilled in the side of the cylinder, in Avhich a glass tube Avas cemented ; through 

 this tube a copper Avire AA\as passed doAvn to the lead, and the rest of the appar- 

 atus was arranged as in the former experiment. When a Leyden jar Avas dis- 

 charged through this apparatus, the needle in the spiral became magnetic, as 

 in the former experiment, showing that electricity during its passage could be 

 AA'ithdraAvn from the center of a solid body. These facts seem to me to be 

 inconsistent Avith the supposition that electrical conduction is confined to the 

 surface of a conducting body. 



As another proof of the theory that conduction of frictional electricity is at 

 the surface of a conductor, Prof. Henry cites the fact that when electricity is 

 throAvn explosively upon a rod Avell connected with the ground, a lateral spark 

 may be drawn from such a rod. To examine this matter an iron rod was 

 brought into good metallic connection Avith a large steam pipe (not in use) 

 Avhich was buried in the ground for more than COO feet of its length, thus secur- 

 ing ample connection with the earth. AVhen electricity was thrown explosively 

 upon this rod from a large prime conductor, a lateral spark could be drawn from 

 any part of the rod, and even from the projecting end of the steam pipe. On 

 passing a metallic rod capjied with a brass ball into the inside of the steam pipe 

 the lateral sjjarlc could lie dravm from the inside of the pipe. This fact seems to 



