Lifting Power of the Electro-Magnet. 297 



vertical by adjusting screws not shown in the figure.* The same iron plate 

 bears the pillar P, also iron, 27-5 inches high, 2 and 1| diameter at its extre- 

 mities, firmly screwed below, and steadied by oblique braces of |-inch round 

 iron (not shown), bolted to the iron at the other end of the table. This bears 

 in rings of hard steel the fulcrum knife-edge of the lever L, which is of spring- 

 steel, ^ thick, 3 deep, tapering to 2 and 1|. Its arms are 21 and 3-5. Its short 

 arm carries by knife-edges the cylinder H, in which is tapped a strong steel 

 screw passing through a hole in the centre of the keeper K, and bearing it by 

 a hemispheric head fitted in a corresponding cavity. The other arm is similarly 

 linked by EE' to a second lever L', whose fulcrum is in the pillar P' 12 inches 

 high. Its arms are 10 and 1 inches ; and at its outer extremity it carries the 

 scale dish S. A sht in the direction of its length enables it to act as a steel- 

 yard, by shifting along it small weights suspended by a loop of fine iron wire ; 

 and for this object it has a division from 1'.9 to 9'.5. The whole apparatus 

 (except the scale) is counterpoised by attaching to L a piece shown in plan, 

 fig. 2, by the screw s and the steady pin t. The box O contains shot, and the 

 ball R, which is tapped on a fine screw, makes the adjustment exact. 



The mode of using this instrument is easily understood. When the magnet 

 is excited, and weights nearly equivalent to its lift are placed in the scale, the 

 screw of the keeper must be turned till a mark on L' stands at the index I. 

 This index, which is hinged to P, so that it can be turned out of the way, shows 

 when the lower edge of the slit in L' is horizontal. Then a check-nut on the 

 screw must be turned into firm contact with H, to preserve this adjustment 



* This arrangement of the magnet did not admit of its being removed, and replaced with the 

 requisite precision ; and latterly it was changed for one which Mr. Bebgin contrived to meet this 

 difficulty. A very strong rectangular frame of brass is secured on the table, 2 inches deep, and 

 able to receive within it the base of the magnet, with an inch play all round. The magnet is 

 slightly excited, so that it may hang freely from its keeper in this space. Then steel screws tapped 

 in the brass, one in front, two behind, and two at the ends of the frame, are brought up so as to 

 pinch the base equally, and thus I am certain that the pull which separates the keeper from the 

 magnet will always be direct. This I find acts most satisfactorily. 



