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. 



Z is a line or string temporarily connecting the ring 2 mth. 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 odier without any twists, as the 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 im- 

 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 e, 

 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 or 

 other parts of the apparatus, while on the orbit-rod, an equal weight 

 should be added to the counterpoise C, to avoid lateral pressure on 

 the pivot e. 



When the elementary particles d, d, are placed in their position 

 the changes of position of the rings should be made gradually to 

 avoid violent blows of these particles upon the ring 1, otherwise they 

 may bruise its edge, or be thrown off with violence, by breaking their 

 supporting threads. 



