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 | 
curvilimear 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 position. 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, $, 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 likewise that of the whole 
system, and the axis of motion of each ring passes through that 
centre. 
eis a pivot to the vertical shaft e f upon which the frame F, 8 
supported, and upon which it may revolve. The axis of this sh 
likewise passes through the centre of the wheel A. 
f is a socket and cone furnished with a tightening screw- 
tis the thumb-screw to fasten and hold the axis ef ig sti) 
becomes necessary to prevent the horizontal motion of the frame *° 
Ps Pp, are two pullies, attached to the two upright pieces of st 
frame by metallic bands, and held fast at any convenient height 0° 
those supports, by screws on the backside. By taking out the sorews 
s, 5, the pullies may be carried below the axis of the outer Dg 
