The New Student's Reference Work/Top

MAXWELL'S DYNAMICAL TOP

Top. The ordinary spinning-top is a rapidly rotating solid supported on a single point below the center of gravity. Suspended in this way the weight of the top acting through its center of gravity exerts a moment of force which tends to tilt the top. The result is that the top “precesses,” instead of falling over, thus exhibiting those phenomena so well-known to every boy of ten. For a detailed explanation of the dynamics of the top consult Worthington's Dynamics of Rotation, chap, xiii, or Perry's Spinning-Tops. Clerk-Maxwell devised a top having more or less the shape of a bell, so that the point of support could be placed at, above or below the center of gravity. It is provided also with adjusting screws as shown in the accompanying figure, so that its mass can be distributed in various ways about the axis of rotation. The chief interest attracting this particular form of top, besides the fact that it most beautifully illustrates the general principles of rotation, lies in the fact that it accurately simulates the motion of our earth on its axis, demonstrating on a small scale the phenomena of precession, nutation, variation of latitude dynamic and static instability etc. Consult Maxwell's original account in his Scientific Papers, Vol. I., pp. 248-68, and a detailed and popular account in The Physical Review, Vol. VI., March, 1898. See Gyroscope.