Experiments upon the Induction of Metallic Coils. 3il 
Leyden jar, which produces a more vivid spark and a sharper snap, 
than a large jar or a battery, in which the quantity of the fluid is in- 
creased, but its intensity diminished. The intensity of the galvanic 
fluid alone is increased by the coil, while its quantity remains the same, 
as is proved by the following experiment. A large galvanometer hav- 
ing a needle two feet long, was connected with a calorimotor of twenty 
four square feet of zinc, charged with a very weak acid. It gave a 
deflection to the needle of 35°. When the charge of this calorimotor 
with the same acid was passed through a coil of zinc ribbon two 
inches wide and one hundred and eighty feet long, the needle of the 
galvanometer still gave the same deviation of 35°. The spark at 
the same time was very vivid, and a shock was felt upon breaking 
the communication, when two handles soldered to the extremities of 
the coil were held in the hands. From this experiment we Jearn 
that the intensity of the electricity alone is increased by traversing a 
coil, and that the quantity of the fluid is not increased or diminished 
by passing through this circuit of one hundred and eighty feet. 
The following experiments were made for the purpose of ascer- 
taining the best method of constructing electro-dynamic magnets by 
means of coils of metallic ribbon. . 
1. A horse shoe of soft iron, twenty four inches long and one inch 
in diameter, was wound with a single covering of zinc ribbon covered 
with silk. When the extremities of the zinc were immersed in the 
cups of a small galvanic battery containing only eighteen square 
inches of zinc, a considerable degree of magnetism was induced in 
the iron. 
2. A ribbon of zinc one inch in width and twenty four feet long, 
was wound around the same iron in small coils of four in thickness 
each, and succeeding each other the whole length of the iron. The 
effect in this experiment was greater than in the last, but not as great 
as I had reason to expect. 
8. The same ribbon used in the last experiment was wound singly 
around the iron and then back again, covering the iron in this way 
with four thicknesses of the zinc, and winding in the same direction 
the whole time. Upon applying the battery, the induced magnet- 
ism was less than in the first experiment. As the rbbon was wound in 
the same direction the whole time, so the tangential direction of the 
revolving force in each layer of the zinc tended constantly 
towards the same pole of the temporary magnet—the result was un- 
expected. But it was doubtless owing to the oblique direction of 
