30 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



causing the approach of the succeeding armature, thus 

 causing rapid motion. Price, $6.00 and $7.00. 



Page's Revolving Magnet. (Fig. 450, next page.) This 

 consists of a U-formed magnet, about eight inches long, 

 supported upright in a mahogany base ; a round piece of 

 soft iron, wound as an electro-magnet with insulated wire, 

 and having a spindle passing through its centre crosswise, and 

 supported in a deep centre below, and above by a milled-head 

 screw, in an arched frame, which is soldered to the ends of 

 the electro-magnet ; the ends of the wires around the electro- 

 magnet are soldered to a Page's pole-changer, which con- 

 sists of two segments of a silver cylinder, about one-third of 

 an inch in length, and one-fifth of an inch in diameter, placed 

 on the opposite sides of the spindle above the electro-mag- 

 net, but insulated from the spindle by its being wound with 

 silk, the segments being separated from contact with each 

 other a small distance. Through the sides of the frames on 

 the poles of the magnet, pass ivory or horn cylinders, insulat- 

 ing stout wires, having at their outer extremities brass cups 

 with binding screws, and within slender silver springs press- 

 ing the cylindrical segments on opposite sides, these seg- 

 ments being placed in such a position as to cause the current 

 to be changed at a proper time to insure the revolution of 

 the electro-magnet, by the attracting and repelling power 

 of the fixed magnet, joined with the like power in the re- 

 volving magnet, occasioned by the battery current flowing 

 through the cups and silver springs, and changing every half 

 revolution, so that while the electro-magnet has one polarity 

 in one half of its revolution, it has an opposite polarity 

 in the other half. In this instrument reversing the poles of 

 the battery in the cups will reverse the motion of the electro- 

 magnet. Price, $6.00 and $7.00. 



Page's Revolving Magnet with Electro- Magnet. (Fig. 

 451, next page.) By substituting an electro-magnet for the 

 permanent magnet, a much more rapid motion may be pro- 

 duced, though the rotation is not reversed by the changing 

 of the poles of the battery current, as in the permanent 

 magnet, owing to its changing the direction of the current 

 in the poles of both electro-magnets ; the revolutions in this 

 instrument are astonishingly rapid, averaging from 5 to 

 100,00 per minute. Price, $6.00 and $7.00. 



