“To the wires _q r_ two other wires are soldered so as to project in an opposite direction, and dip into the thimbles _l m_. The wires of the galvanic magnet have thus, as it were, four projecting ends; and by inspecting the figure it will be seen that the extremity _p_, which dips into the cup _m_, attached to the copper of the battery in G, corresponds to the extremity _r_ which dips into the cup _t_, connecting, with the zinc in battery F. When the batteries are in action, if the end B is depressed until _q r_ dips into the cups _s t_, A B instantly becomes a powerful magnet, having its north pole at B; this, of course, is repelled by the north pole D, while at the same time it is attracted by C; the position is consequently changed, and _o p_ comes in contact with the mercury in _l m_; as soon as the communication is formed, the poles are reversed, and the position again changed. If the tumblers be filled with strong diluted acid, the motion is at first very rapid and powerful, but it soon almost entirely ceases. By partially filling the tumblers with weak acid, and occasionally adding a small quantity of fresh acid, a uniform motion, at the rate of seventy-five vibrations in a minute, has been kept up for more than an hour; with a large battery and very weak acid the motion might be continued for an indefinite length of time.” Following Prof. Henry came Sturgeon’s rotary motor of 1832, Jacobi’s rotary motor of 1834, Fig. 29, which had electro-magnets both in the field and armature; Davenport’s motor of 1834, Zabriskie’s motor of 1837, in which a vibrating magnet converted reciprocating into rotary motion; Davenport’s motor of 1837 (U. S. Pat. No. 132, Feb. 25, 1837), Fig. 30; Page’s rotary motor of 1838, Walkley’s motor of 1838 (U. S. Pat. No. 809, June 27, 1838); Stimson’s motor of 1838 (U. S. Pat. No. 910, Sept. 12, 1838); Page’s motor of 1839, Cook’s of 1840 (U. S. Pat. No. 1,735, Aug. 25, 1840); Elias’ motor of 1842, invented in Holland; Lillie’s motor of 1850 (U S. Pat. No. 7,287, April 16, 1850); the Neff motor of 1851 (U. S. Pat. No. 7,889, Jan. 7, 1851), of which illustration is given in Fig. 31, and Page’s motor of 1854 (U. S. Pat. No. 10,480, Jan. 31, 1854). In 1835 Davenport constructed a small circular railway at Springfield, Mass. [Illustration: FIG. 29.--JACOBI’S ROTARY ELECTRIC MOTOR.]