the particles of magnetic bodies , &c. 73 
C D passing through it, to which a rapid rotation can be 
given by means of the handle E F, to the axis of which, 
under the table, a wheel is attached, having a band passing 
round the lower part of the axis CD. I11 the upper and 
under sides of the wooden frame G H, firmly screwed on the 
axis CD, are openings in which the brass frames a, a , a xi a t) 
slide, and can be clamped at any distance from the axis, by 
means of milled headed screws passing through them, and 
working in brass nuts, holding on each side of the slits. In 
the brass frames a , a, a ti a ti are square openings to admit 
the magnets S N, S, N t , either with their faces or their edges 
towards the axis of rotation, and in which they can be firmly 
wedged. By this means the distance from the axis of rota- 
tion at which the magnets revolve, and likewise the verticality 
of their axes, can be very accurately adjusted. From the 
handle E F, a brass spring b projects, and this striking on 
two small elevations c, c t , diametrically opposite to each other 
on the table, indicates very accurately the time of half a 
revolution, I K is a tube fixed to the ceiling of the room at 
I, and having a clamping screw at K, by which the tube L M, 
sliding within the other I K, can be fixed. The suspending 
wire ef is nipped tightly in a piece of slit brass by means of 
the screw d. The lower end of the suspending wire is simi- 
larly fixed between two small flat pieces of brass, which, 
below, form a broad stirrup, into which small wires, from 
the angles of a light rectangular wooden scale, may be passed, 
and there crossing each other, any torsion of the suspending 
wire immediately acts upon the scale, and vice versa. From 
the suspended scale a small piece of brass projects, which 
indicates in circles and degrees, on a large graduated ring, 
MDcccxxvn. L 
