Lectures de Potentia Restitutiva, or of Spring

That is, if weight F stretches the spring so that the bottom of the scale descends to o, then weight G will make it descend to p, H to q, I to r, K to s, L to t, M to u, and N to w, and so on. So that the distance x o shall be one space, x p two spaces, x q three, x r four, x s five, x t six, x u seven, and x w eight.

The second figure represents a watch spring coiled in a spiral, labeled CABBBD. Its end C is fixed to an immovable pin or axis. Into the end of this axis, the axle of a small, light wheel is inserted, upon which it moves. The other end of the spring, D, is fixed to a pin in the rim of the wheel y y y y. Around this wheel is coiled a small silk thread, to the end of which is fixed a scale original: "Scale"; a weighing dish or pan to receive the weights. To the frame containing these parts is fixed a hand or pointer original: "Index" z. Then, testing with the same weights put into the scale E, you will find that if weight F sinks the bottom of the scale x to position o, then G will sink it to p, H to q, I to r, K to s, and L to t; and the pointer z will point at 1, 2, 3, 4, 5, 6, 7, 8 on the wheel.

The trials with a straight wire, or a straight piece of wood laid horizontally, are so plain they do not need an explanation by a diagram. The method of testing this principle on air I have long ago explained in my Micrographia Robert Hooke's famous 1665 book on microscopy and science with illustrations.

From all of this, it is very evident that the Rule or Law of Nature in every springing original: "springing"; elastic body is this: the force or power it exerts to restore itself to its natural position is always proportionate to the distance or space it is removed from that position. This holds true whether the removal is by rarefaction original: "rarefaction"; stretching or thinning out (the separation of its parts from one another) or by condensation (the crowding of those parts closer together). Nor is this only observable in these specific objects, but in all other elastic bodies whatsoever, whether metal, wood, stones, baked earths ceramics, hair, horns, silk, bones, sinews, glass, and the like—provided respect is paid to the particular shapes of the bodies being bent, and the advantageous or disadvantageous ways of bending them.