506 Prof. J. Henry's Contributions 



electricity in a long conductor is always somewhat greater than 

 in a short one. 



T*. Let us, however, in order to simplify the conditions of 

 the induction at the ending of a current, suppose that the 

 quantity in a unit of the conductor is inversely as its whole 

 leno-th, or, in other words, that the quantity of current elec- 

 tricity is the same in a long conductor as in a short one ; and 

 let us also suppose, for an example, that the length of the spiral 

 conductor, fig. 3, was increased from one spire to twenty 

 spires ; then, if the velocity of the diminution of the section of 

 the current is the same (69.) in the long conductor as in the 

 short one, the shock which would be received by submitting 

 the helix to the action of one spire of the long coil would be 

 nearly of the same intensity as that from one spire of the short 

 conductor; the quantity of induction, however, as shown by 

 the galvanometer, should be nearly twenty times less; and 

 these inferences I have found in accordance with the re- 

 sults of experiments (75.). If, however, instead of placing the 

 helix on one spire of the long conductor, it be submitted at 

 once to the influence of all the twenty spires, then the inten- 

 sity of the shock should be twenty times greater, since twenty 

 times the quantity of current electricity collapses, if we may 

 be allowed the expression, in the same time, and exerts at once 

 all its influence on the helix. If, in addition to this, we add 

 the consideration, that the whole quantity of current electricity 

 in a louCT conductor is greater than that in a short one (73.), 

 we shall have a further reason for the increase of the terminal 

 shock, when we increase the length of the battery conductor. 



75. The inference given in the last paragraph, relative to 

 the change in the quantity of the induction, but not in the in- 

 tensity of the shock from a single spire, by increasing the 

 whole length of the conductor, is shown to be true by repeat- 

 ino' die experiment described in paragraph 13. In this, as we 

 have seen, the intensity of the shock remained the same, al- 

 thouo-h the length of the circuit was increased by the addition 

 of coil No. 2. When, however, the galvanometer was em- 

 ployed in the same arrangement, the whole quantity of in- 

 duction, as indicated by the deflection of the needle, was di- 

 minished almost in proportion to the increased length of the 

 circuit. I was led to make this addition to the experiment 

 (13.) by my present views. 



76. The explanation given in paragraph 74 also includes 

 that of the peculiar action of a long conductor, either coiled 

 or extended, in giving shocks and sparks from a battery of a 

 single element, discovered by myself in 1831 (see Contrib. 

 No. II.). The induction, in this case, takes place in the con- 



