1831] WRITINGS OF JOSEPH HENRY. 51 



iron three inches square and thirty inches long. Before 

 bending the bar into the shape of a horse-shoe, it was flat- 

 tened on the edges, so as to form an octagonal prism, having 

 a perimeter of lOf inches. The other dimensions of the 

 magnet, as measured before winding it with wire, arc as fol- 

 lows: — perpendicular height of the exterior arch of the 

 horse-shoe, 11| inches; around the outside from one pole to 

 the other, 29y^^ inches; internal distance between the poles, 

 3^ inches. 



The armature or lifter is formed from a piece of iron from 

 the same bar, not flattened on the edges; it is nearly 3 

 inches square, 9^ inches long, and weighs 23 lbs. The 

 upper surface is made perfectly flat, except about an inch 

 in the njiddle where the angles are rounded off so as to form 

 a groove, into which the upper part of a strong iron stirrup, 

 surrounding the armature, fits somewhat loosely. The 

 weight to be supported is fastened to the lower part of the 

 stirrup, and by means of the groove is made to bear directly 

 on the centre of the armature. 



For the purpose of suspending the magnet, a piece of 

 round iron with an eye on one end, is firmly screwed into 

 the crown of the arch and is attached to the cross beam of a 

 frame, similar to that figured in the last number of the 

 Journal. 



The magnet is wound with 26 strands of copper bell-wire, 

 covered with cotton thread 31 feet long ; about 18 inches of 

 the ends are left projecting, so that only 28 feet actually sur- 

 round the iron ; the aggregate length of the coils is there- 

 fore 728 feet. Each strand is wound on a little less than an 

 inch ; in the middle of the horse-shoe it forms three thick- 

 adequate to decompose water, since it might under these circumstances be 

 attributed to the electricity from the battery, I had determined in a second 

 experiment, had the first proved successful, to have interrupted the galvanic 

 flow by a non-conductor; in which case, had the decomposition ensued, 

 pure magnetism might have been considered as the decomposing agent. 

 But as my preliminary experiment was unsuccessful, I proceeded no farther; 

 I hope, however, to resume the research hereafter, under more favorable cir- 

 cumstances. C. U. Shepard.] 



