DISCOURSE OF W. B. TAYLOR. 247 



perfectly insulated near conductor could be obtained more intense 

 than the primary shock directly from the jar. * 



These investigations having in view the discovery of " inductive 

 actions in common electricity analogous to those found in galvanism" 

 (commenced in the spring of 1836), led to renewed examination of 

 the secondary galvanic current, which since November 24th, 1831, 

 (or for seven years,) had received no special attention. Henry's 

 very interesting series of experiments were detailed in a somewhat 

 elaborate memoir read before the American Philosophical Society, 

 November 2nd, 1 838. Employing five different sized annular spools 

 of fine wire (about one-fiftieth of an inch thick) varying from one- 

 fifth 1 of a mile to nearly a mile in length (which might be called 

 "intensity" helices); and six flat spiral coils of copper ribbon vary- 

 ing from three-quarters of an inch to one inch and a half in width, 

 and from 60 to 93 feet in length (which might be called " quantity " 

 coils), he was able to combine them in various ways both in con- 

 nection and in parallelism. A cylindrical battery of one and three- 

 quarters square feet of zinc surface was principally used ; and the 

 galvanic circuit was interrupted by drawing one end of the copper 

 ribbon or wire over a rasp in good metallic contact with the other 

 pole of the battery. 



From the energetic action of the flat ribbon coil in producing 

 the induction of a current on itself, it was inferred that the second- 

 ary current would also be best induced by it. With the single 

 larger ribbon coil in connection with the battery, and another ribbon 

 coil placed over it resting on an interposed glass plate, at every 

 interruption of the primary circuit an induction spark was obtained 

 at the rubbed ends of the second coil ; though the shock was feeble. 

 With a double wire spool (one within the other) of 2650 yards, 

 placed above the primary coil (having about the same weight as the 

 copper ribbon) the magnetizing effects disappeared, the sparks were 

 much smaller, "but the shock was almost too intense to be received 

 with impunity." The secondary current in this case was one of 

 small "quantity" but of great "intensity." With a single break 

 of circuit in the primary, it was passed through a circle of 56 stu- 

 dents of his senior class, with the effect of a moderate charge from 



* Proceedings Am. Phil. Soc. May 4, 1838, vol. I. p. 14. 



