363 STATE BOARD OF AGRICULTUEE. 



gas-pipe or guu-barrol? This question was submitted to esperimeiit as follows : 

 Two spirals having the same number of coils were formed from the same piece 

 of wire; in the axis of these spirals two needles as nearly alike as possible were 

 placed ; one of these spirals was placed in a long glass tube (to insure more 

 perfect insulation), and this tube was placed inside a gas-pipe ; the other spiral 

 was outside the gas-pipe and a few inches from it; two ends of the wire were 

 then made clean and bright, twisted together and capped with a brass ball; the 

 other two ends were also made clean and bright, twisted together, and con- 

 nected with the outside coating of the battery of Leydon jars. 

 Cut II. exhibits this arrangement. 



FH 



Here two pei'fectly equal paths were open for the passage of electricity, and 

 if a charge were passed from + to - the electricity would divide and equal 

 amounts pass by each conductor and the needles in both spirals would exhibit 

 the same amount of magnetic intensity unless the iron tube exerts a modifying 

 influence over the magnetizing power of the internal spiral. The experiment 

 was tried repeatedly, and uniformly the needle in the internal spiral was 

 inferior in magnetic intensity to the needle in the external spiral, usutdly in the 

 proportion of 2 to 5. 



We thus see that the conditions attending Prof. Henry's experiment, instead 

 of the simplicity which they at first sight seemed to have, were in fact quite 

 complex. The intensity of magnetism developed in the needle in ihe interior 

 spiral" cannot be accepted as a true measure of the amount of electricity which 

 passed through the interior wire- 

 Prof. Henry concedes that galvanic electricity has little or no repulsive 

 energy, and passes through the whole substance of the metallic rod. The 

 question then arose, can galvanic electricity be made to exhibit a similar tend- 

 ency to surface action? To render the answer decisive the conditions of 

 experimental proof were purposely made such as would favor an answer in the 

 negative. A half -inch gas -pipe was used for the internal conductor; outside 

 this was placed a long glass tube, covered for five-sixths of its length with tin- 

 foil for the external conductor ; the tin-foil embraced the gas-pipe at one end, 

 while the other end of the foil terminated in a long copper wire which was 

 coiled into a magnetizing spiral, and a very sluggish galvanometer was also 

 introduced into this part of the circuit to measure the intensity and the direc- 

 tion of the flow of electricity; the wire from this exterior circuit was twisted up 

 with a wire prolonging the gas-pipe. Cut III. will show the arrangement for 

 this experiment, 

 + 



III 



