Description of the Rotascope. 271 
u, u, are nuts to keep in place the upper piece of the frame. Their 
heads are perforated to receive cords for suspending the frame when 
necessary. 
M, M, represent moving forces applied to the cord a, to give a 
rapid motion to the wheel. To know precisely what forces are ap- 
plied to this cord, in experiments requiring the measure of those 
forces, we detach the weights W, W, and their cords c, ¢, bring down 
the pullies p, p, nearly to the screws s, s, and turning the rings into 
such a position that the cord a will go over the pullies, substitute 
weights of equal magnitudes at M, M, instead of the hands of the 
experimenter. A double series of weights from two to thirty two 
ounces accompanies the instrument. Each is furnished with a hook 
at top, and a small conical pin at bottom; the latter serving the 
double purpose of keeping them in place when deposited on the base 
of the stand, as seen in the figure, and of attaching them expedi- 
tiously to the rings 1, 2, by means of holes drilled to receive them. 
A weight thus attached is seen at g, Fig. 2. 
The cord a, is attached to the axis by means of the small project- 
ing conical knob k, k, one of which is near each end of the shaft. 
centre of the cord is doubled, and the pin applied to the doub- 
led part, the wheel is then set in motion to wind up the cord, so that 
one end will be drawn off from above, the other from below, and 
both tend to turn the wheel in the same direction. 
_%¢, are two cords connected with a small pulley on the axis of 
tng 1, and passing over the pullies p, p. 
» W, are weights attached to this cord. 3 
“indicates the direction in which those weights tend to turn the 
denotes the direction in which the wheel will move when actu- 
ated by the forces M, M, as here represented ; but by turning the 
Wheel in the opposite direction, when the cord is applied over the 
knob, the wheel will be put in motion in the opposite direction. 
isa bar of mahogany called the orbit-rod, with a socket f, by 
Means of which it may, when the frame F, is removed, be placed 
™ the Pivot e, and made to revolve. In this case, the frame con- 
Mining the wheel, is to be set or suspended at one end, while at the 
~ is suspended the weight C, which exactly eounterpoises the 
“ame and its appurtenances. This weight is placed below the bar 
order to bring the centre of gravity as low as practicable, and pro- 
Nee a more stable equilibrium. 
