Electro-Magnetic Rotations. 129 



copper and two inches wide, may be nearly two hundred feet 

 long, before we reach its maximum length. If this ribbon be half 

 an inch wide, the magnet which it is employed in constructing, 

 will lift more if we have two lengths of sixty feet each, than if 

 we employ one hundred and twenty feet in one ribbon. With 

 four ounce copper, one inch wide, fifty feet was the greatest 

 length employed, and when the copper foil weighed two ounces 

 to the square foot, about twenty-five feet was found to be the 

 maximum length. 



Abt. XYII. — Electro- Magnetic Rotations ; by John B. Zabris- 

 KiE, M. D., of Flatbush, N. Y. 



Electro-Magnetic rotations may be considered as of two 

 kinds. 1st. Those where the motion is produced by changing 

 the poles of one magnet or system of magnets, when they come 

 opposite to the poles of another magnet or system of magnets. 

 2d. Where a magnet or conductor is moved by the tangential 

 force of an electric current. 



The power of the first class is greater than that of the other 

 with the same weight of metal, and the same battery power, for 

 although the effect of the electrical current, especially when pas- 

 sing through a helix or flat spiral resembles, that of a magnet, 

 still it is not equal to the attraction and repulsion of the contig- 

 uous poles of powerful magnets. 



The following experiments contain an application of the tan- 

 gential force operating in a manner never yet described. 



In the winter of 1836, I made the following experiment. A 

 metallic ribbon, 180 feet long and two inches wide, was formed 

 into an oblong coil, so as to encircle a large compound magnet 

 two feet long which was suspended freely upon an axis within 

 the coil of ribbon. Upon connecting the extremities of the 

 ribbon with the poles of a galvanic battery, the magnet was im- 

 mediately thrown at right angles to the coil, when a lever moved 

 by the revolving magnets turned an apparatus which changed the 

 direction of the galvanic current in the metallic ribbon. The 

 rotation was thus continued until the magnet reached the revolu- 

 tion of half a circle, when the direction of the current was again 

 changed. 



Vol. sxsvi, No. 1.— Jan.-April, 1839. 17 



