"This instrument is similar to Page's Revolving Ring, a rectangular coil of wire being substituted for the ring. The rotation is much more rapid in consequence of the proximity of the rectangle to the magnet, not only near by poles, but throughout the greater part of its length. By this means the great speed of eight or ten thousand revolutions in a minute may be attained." (from the 1842 edition of the Manual of Magnetism, pg 98. 

   This instrument is a version of the Electro-dynamic Revolving Rectangle.