now seen to be merely the tendency of a revolving body to move in a
straight line, and the resistance which it opposes to being drawn aside
from that line. Simple enough! But when we come to consider this action
carefully, it is wonderful how much we find to be contained in what
appears so simple. Let us see.

[Footnote 1: I was led to study this subject in looking to see what had
become of my first permanent investment, a small venture, made about
thirty-five years ago, in the "Sawyer and Gwynne static pressure
engine." This was the high-sounding name of the Keely motor of that day,
an imposition made possible by the confused ideas prevalent on this very
subject of centrifugal force.]

FIRST.--I have called your attention to the fact that the direction in
which the revolving body is deflected from the tangential line of motion
is toward the center, on the radial line, which forms a right angle with
the tangent on which the body is moving. The first question that
presents itself is this: What is the measure or amount of this
deflection? The answer is, this measure or amount is the versed sine of
the angle through which the body moves.

Now, I suspect that some of you--some of those whom I am directly
addressing--may not know what the versed sine of an angle is; so I must
tell you. We will refer again to Fig. 1. In this figure, O A is one
radius of the circle in which the body A is revolving. O C is another
radius of this circle. These two radii include between them the angle A
O C. This angle is subtended by the arc A C. If from the point O we let
fall the line C E perpendicular to the radius O A, this line will divide
the radius O A into two parts, O E and E A. Now we have the three
interior lines, or the three lines within the circle, which are