The earths **precessional** motion is of this latter type, the angles being ci = .0087, ~=23 28.

The polhode and herpoihode cones are then right circular, and the motion is **precessional** according to the definition of 18.

We can hence deduce the condition of steady **precessional** motion in a top. A solid of revolution is supposed to be free to turn about a fixed point 0 on its axis of symmetry, its masscentre G being in this axis at a distance h from 0.

If we put Oso we get the condition of steady **precessional** motion in a form equivalent to (3).

The theory of disturbed **precessional** motion there outlined does not give a convenient view of the oscillations of the axis about the vertical position.

This fundamental advance rendered inevitable the detection of **precessional** effects.

They have an apparent **precessional** movement, the exact amount of which can be arrived at only by prolonged and toilsome enquiries.