Electro-Magnetic Rotations. 



131 



first well covered with silk so as completely to insulate them from 

 each other, and from the tube. A stout iron wire firmly riveted 

 to the magnet passes through the tube and being fastened to the 

 frame by a screw serves to suspend the magnet. The ribbon C 

 D is wound over a thin frame of wood and each extremity sold- 

 ered to a semicircular strip of copper, forming when applied to 

 the lower axis, a pole changer similar to those of Dr. Page, this 

 pole changer is placed so as to change the direction of the cur- 

 rent in the revolving ribbon when it is at right angles to the 

 magnet. The extremities of the wires E F press upon the se- 

 micircular strips of copper, and thus when a communication is 

 made between each of these wires, and the poles of a battery 

 they transmit a currunt both to the ribbon and to the magnet. 

 The ribbon will be found to move immediately to a position at 

 right angles to the magnet, and when it arrives at that point, the 

 direction of the current is changed by the pole changer, the mo- 

 tion is continued, and thus a constant rotation is obtained. 



The same experiment is reversed by making a galvanic mag- 

 net rotate within a coil of metallic ribbon changing the poles of 

 the magnet when at right angles to the coil by means of the pole 

 changer. 



The following (Fig. 3,) is a powerful machine acting upon this 

 principle. A and B are two galvanic magnets each one foot m 

 length, fixed upon the axis E, and turning freely within a wooden 



Figure 3. 



=F=F 



frame, around which is coiled the ribbon C D. The strip of 

 copper F conveys the electrical current to the wires upon the gal- 

 vanic magnets A and B, through two pole changers, one for each 



