The resistance to motion round a curve has not been so systematically studied that any definite rule can be formulated applicable to all classes of rolling stock and all radii of curves.
Propositions I-II are preliminary, 13-20 contain tangential properties of the curve now known as the spiral of Archimedes, and 21-28 show how to express the area included between any portion of the curve and the radii vectores to its extremities.
It is the envelope of circles described on the central radii of an ellipse as diameters.
In diameter, sometimes surmounted by trees in the midst of a treeless plain and sometimes arranged in circles and on radii, and decreasing in size with distance from the centre of the field - has been variously explained.
The law, e.g., of the equality of the radii of a circle cannot be exhibited to sense, even if equal radii may be so exhibited.