An account of the Electro- Magnetic Engine. 125 



pelled by electro-magnetism, is said to have already applied some 

 smaller ones to different objects, such as the working of printing- 

 presses, principally of a few horse power. As Davenport's machines 

 are at present the most powerful and simple, it is but fair to give a des- 

 cription of them here. 



1. Rotatory machines, consisting of moveable electro-magnets and 

 stationary magnets. 



The moveable part of this machine consists of two horizontally- 

 placed iron bars, crossing each other at right angles. They are both 

 fifty-two inches long, and pass at each end into a spherical segment of 

 soft iron. The sectors of each of these segments are three inches long, 

 and their position horizontal, being attached to the iron rods. 



This iron cross rests upon a perpendicular axle, round which it moves 

 with ease : the iron cross-poles are encircled with coils of copper wire, 

 round which cotton has been spun ; and they may be brought in 

 connection with a small battery consisting of concentric copper and 

 zinc cylinders, which can be inserted in a quart of diluted acid. Two 

 semicircles of strongly magnetized iron form a circle, except at the 

 opposite poles ; and within this horizontal circle the galvanized iron 

 cross moves, so that its iron segments move parallel, and close to 

 the magnetic circle, and likewise in the same plane. Its axis is pro- 

 vided at the upper end with a cog-wheel, on whose horizontal axle 

 weights are suspended, which are raised by the coiling of a rope. As 

 soon as the battery is duly provided with diluted acid, and set in 

 connection with the machine, the action and motion commence, by 

 means of the iron cross revolving with its segments or flanks By 

 means of the galvanic battery, the crosses and segments are mag- 

 netized ; in other words, they acquire at their opposite extremities 

 positive and negative polarity ; and as they are exposed to the powers 

 of attraction and repulsion of magnets fastened in a circle, a rapid 

 horizontal motion necessarily ensues. 



If the battery be small, 200 to 300 revolutions take place in one 

 minute, and 600 if a larger one be employed. The rope with a 141bs, 

 weight attached, was coiled up, and 28lbs. raised from the ground. 

 The motion instantly ceases, on the connection with the. battery being 

 interrupted ; and it may be reversed by merely making the wires of the 

 battery change place with those of the machine : the motion then 

 takes place with the same rapidity, but in a contrary direction. 



2. Rotatory machines consisting solely of electro-magnets. 



Mr. Davenport exhibited a machine of this kind in New York, 

 March, 1837. The only difference between it and the one just describ- 



