552 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



by joining the fnagnets again, a current will be developed in op- 

 posite direction; if desired, those two currents may of course 

 be led in the same direction by the ingenious contrivance, well 

 known as the commutators, attached to the same IcA^er. 



About the three different kinds of magneto-electric apparatus 

 mentioned above, under 9, 10, I wish to observe that all experi- 

 menters, even those who made the largest, did (as far as I have 

 been able to find out) seek more for power in a great number of 

 coils and magnets, than in a single one or a single pair of very 

 large size, and by this made an isolation as perfect as that in the 

 Rumhkorf coil, an impossibility. 



The largest apparatus of this kind I met with was one im- 

 ported from England, intended to produce electric light; it con- 

 sisted of a few hundred tolerably sized steel magnets and some 

 eighty or one hundred small coils, of the most unphilosophical 

 construction ; it required at least three or four horse power to 

 run it, and the only thing to which those who had charge of it — 

 and by the way who proved not to understand much of electric 

 science — could turn this large apparatus into account, was in 

 electro-plating, to an amount equal to that accomplished by a 

 common battery, at the expense of the consumption of a few 

 ounces of zinc. A company was formed to electroplate in this 

 way; a small bungled imitation of the large apparatus made its 

 appearance at one of the exhibitions of the American Institute, 

 at the Crystal Palace, and, of course, the company soon wound 

 up with considerable loss, except perhaps to its director, Mc S., 

 who departed. I do not here assert that this way of electro- 

 plating or electro-typing is impracticable, but a small apparatus, 

 moved by a very small fraction of a horsepower, will accomplish 

 it, and may, in some peculiar circumstances where there is powder 

 to waste, be used with profit. However, if one uses a common 

 Smee battery and sells the products of his battery, the sulphate 

 of zinc, he will very nearly be compensated for the common sul- 

 phuric acid and metallic zinc, and his electric current will cost 

 him very little. 



Suppose that Rumhkorf, instead of making his large magnifi- 

 cent apparatus of one single coil, had constructed fifty or one 

 hundred small induction machines like they that are used in 

 medicine, or a little larger, and had connected them to receive 

 the current of all, would he have retained such glorious results 

 as by winding all the wire in one single coil, thus securing larger 



