Experiments wpov, the Induction of Metallic Coils. 311' 



Leyden jar, which produces a more vivid spark and a sharper snap, 

 than a large jar or a battery, in vs^hich 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 learn 

 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. 



3. 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 ribbon was wound in 

 the same direction the whole time, so the tangential direction of the 

 revolving magnetic 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 



