Asai kindness Calle ws 
involved much friction and unstableness. In the representation, 
the parts are of very different proportions fr m those of the instru- 
ment in actual use; the object 0 ing the curves of such short 
radii being to contract the drawing. ‘The coil of copper wire A 
is made upon a circular for- 
mer, consisting of a bent rod 
about one fourth of an inch 
in diameter. The piece of 
soft iron wire E is less than 
one eighth of an inch in 
diameter, and is bent so as 
to be concentric with the 
coil. It is counterpoised by 
a brass wire F of similar 
form, and extending about 
half through the coil, the 
dividing line being shown _ 
half; way. The soft. iron | ity + 
wire should be of greater oe) 
length than the coil, so that when the bend of the wire at R is in 
contact with the extremity of the coil, its ends should project 
some distance from the opposite extremity. aa 
The extremities of the coil of wire are connected with binding 
screws P. he index point R shows upon the scale H the de- 
gree of force exerted, in absolute weight. The frame of soft iron 
and brass wires is braced and suspended by the wire rods G, G, the 
whole moving freely upon the centre O. Above this is raised a 
stem with a regulating weight, by which the sensitiveness of the 
instrument may be increased or diminished at pleasure. The 
coil is firmly secured to a concentric bed-piece or block B, which 
slides upon a concentric shelf or projection C, and is fixed at any 
desired point by means of the set screw D, passing through a slit 
in the shelf C. By moving the coil back or forth upon the slide, 
the sensitiveness of the instrument may also be diminished or in- 
creased at pleasure. The position of equilibrium between the 
coil and wire, is when the bend R of the wire is in contact with 
the coil, but the point of greatest action is when the extremities 
of the wire about coincide with the dotted line S. Therefore if 
the coil be so adjusted that this line shall be under the dividing 
line in the centre of the frame, the serisitiveness is at a maximum. 
