MAGNETO-ELECTRIC MACHINES. 45 



armatures when the latter are revolving. The poles of the U-shaped 

 magnets are, on the contrary, as nearly as possible in contact with 

 the armatures which revolve within the circle formed by them, 

 either between the poles or in front of them. Instead of the bars 

 which form the circle being of steel and magnetized, they may be 

 made of soft iron, and depend for their magnetism upon the magnetic 

 bars before-named placed around them. In another form of machine, 

 both the magnets and armatures are stationary, and the commutator 

 alone has motion between the poles of the horse-shoe magnets and 

 the armatures being mounted on a spindle and caused to revolve by 

 a band from some driving machinery. The commutator, or break- 

 piece, is composed of a brass centre, with four radial arms of soft iron, 

 either solid or formed of two or more plates." See Repertory of Pa- 

 tent Inventions, vol. 18th, for 1851, and Sketches therein. 



The quality of these machines for depositing depends much upon 

 their sustaining power. Eight of these sets of plates or magnets, 

 containing altogether about 12 cwt. of steel, in a proper state of 

 working, form a battery capable of depositing from 12 to 20 ounces 

 of silver per hour ; and, as the plan of the machine is new, and may 

 be still further improved, the relative economy of these magnets and 

 the galvanic battery is not yet fully ascertained. We have, however, 

 no doubt that, as such a machine gives electricity of great intensity, 

 it may be superior to the galvanic battery for some purposes, and 

 may give properties to the deposited metals which the ordinary 

 battery does not. 1 



Before concluding the description of batteries, we may briefly 

 notice one or two little conveniences which are indispensable to the 

 operator. The first of these is what are termed binding screws, by 

 which the parts of 

 batteries, as we 

 have shown by nu- 

 merous figures, are 

 connected toge- 

 ther, or by which 21. 22. 23. 24. 25. 26. 

 their poles are con- 

 nected to the objects through which the voltaic current is to be 

 passed. They are usually made of brass, and of various forms, 

 according to the shape of the objects that are to be connected. 



Figures 21 to 26 represent some of the most useful kinds ; fig. 21 

 is used to connect wires together ; figs. 24 and 26 are required for 

 Smee's battery (see fig. 18); fig. 25, to connect the plates of Grove's 



1 For some particulars of the working of electro-magnetic machines, see Shaw's 

 Manual of Electro-Metallurgy, 2d edition, 1843. 



