272 Description of the Rotascope. 
d, d, are two small metallic beads suspended to the axis by delicate 
threads, at about one inch distance on each side of the nave of the 
wheel A. When the wheel is in rapid motion, these metallic parti- 
cles revolve in planes parallel to it. But when any new force tends 
to change the position of its plane, they will be seen to persist for a 
time in the planes which they have acquired ; by which means they 
become indexes of the tendencies of the particles of the wheel itself, 
while under the influence of such new force. 
1 isa line or string temporarily connecting the ring 2 with the upper 
part of the frame F. 
The following directions and cautions will be found serviceable in 
using the Rotascope. 
In winding up the moving cord around the axis of the wheel, it is 
necessary to keep the two parts as near to each other as practicable 
without having one overlie, or actually rub against the other, and to 
have them wound from the beginning to the end of the spiral, parallel 
to each other without any twists, as latter will materially obstruct 
the uncoiling, when the force is applied, and endanger the breaking 
of the cord. Care should be taken that the uncoiling be made in 
such a position of the rings that the moving cord will free itself sm- 
mediately from all contact with the wheel, at the instant it leaves the 
shaft. 
The cords applied to the several pullies on the first and second 
rings, should be kept closely wound up round their respective pullies 
when not wanted for immediate use, as they may otherwise become 
entangled in the wheel, and obstruct its motion, or essentially endan- 
ger the accuracy and safety of the whole instrument. 
In using the orbit-rod, the weight should be attached first, then the 
frame F, put in its place, and finally the socket set upon the pivot ¢ 
when the base B, will sustain the whole. ‘The revolutions should 
begin’ with a slow motion and increase in velocity ; all shocks and 
sudden changes of motion should be avoided. : 
When it becomes necessary to add any weights to the rings 
other parts of the apparatus, while on the orbit-rod, an equal weight 
should be added to the counterpoise C, to avoid lateral pressure 0” 
the pivot e. 
When the elementary particles d, d, are placed 
the changes of position of the rings should be ma 
avoid violent blows of these particles upon the ring 1, sa lt 
may bruise its edge, or be thrown off with violence, by breaking * 
supporting threads. 
