270 Description of the Rotascope. 



From the foregoing facts and observations, the importance of some 

 apparatus to illustrate and, if practicable, to measure the tendency 

 of bodies in rotation to preserve or to alter their planes of motion, 

 and also to exhibit the various effects of combining a progressive 

 curvilinear motion with rotation about a certain axis, will be obvious. 



It is believed that no instrument heretofore presented to the public 

 has been constructed for this especial purpose. 



The following description refers to the accompanying plate. 



A is a fly-wheel about eight inches in diameter, formed in such a 

 manner as to receive but slight resistance from the air. It is support- 

 ed on the centre of a perfectly cylindrical axis about three eighths of 

 an inch in diameter, terminated by cones to serve as pivot points, on 

 which the wheel runs. The wheel is of brass, the axis of steel, one 

 end, from the wheel toward the pivot, being polished, the other bron- 

 zed, for more readily distinguishing the changes of poshion. The 

 wheel with its axis weighs about two pounds and eleven ounces. 



B is the base, or tripod which sustains the instrument. 



F is a wooden frame containing the principal moving parts of the 

 apparatus. 



1, 2, 3, are concentric metallic circles, or rings, each about three 

 fourths of an inch in breadth, and about two tenths of an inch in 

 thickness. The exterior one (3), being about fifteen inches exterior 

 diameter, is sustained in its place by the screws s, s, which have their 

 ends conically excavated to receive the pivots. 



The axis of the next ring (2), is at right angles to that of 3 and 

 again the axis of 1 is at right angles to that of 2, and the axis of the 

 wheel A, to that of the ring 1. 



The centre of gravity of the wheel is likev^^ise that of the whole 

 system, and the axis of motion of each ring passes through that 

 centre. 



e is a pivot to the vertical shaft ef upon which the frame F, is 

 supported, and upon which it may revolve. The axis of this shaft 

 likewise passes through the centre of the wheel A. 



/ is a socket and cone furnished with a tightening screw. 



t is the thumb-screw to fasten and hold the axis ef whenever it 

 becomes necessary to prevent the horizontal motion of the frame F. 



p, p, are two pullies, attached to the two upright pieces of the 

 frame by metallic bands, and held fast at any convenient height on 

 those supports, by screws on the backside. By taking out the screws 

 5, s, the pullies may be carried belov) the axis of the outer ring. 



