On the Movement of Animals, Part Two

With the rope AB being extended directly by the weight Z, since in the first corrugation C the two contrary powers S and R are shown b Per anteced. Schol. to be quadruple of the resistance Z: but these same powers effect nothing other than the shortening of the rope, and therefore they act in the same way as if the rope had been knotted at point C by some bond, and had been affixed to a nail X, and extended directly below C as far as B by the weight Z. Let two other contrary powers H and I subsequently supervene, effecting a second complete contortion D: and because the upper part of the rope DCA remains tensed, notwithstanding the intermediate corrugation C; and likewise the lower portion DB is tensed by the weight Z; therefore the two contrary powers H and I will be quadruple of the same resistance Z: wherefore the four powers S, R, H, and I taken together will be octuple of the resistance Z. The same must be said of the remaining corrugations E and F: therefore the quadruple of the resistance Z must be taken as many times as there are corrugations, etc.

Hence it is evident that the entire corrugated length of the rope is indeed pushed upward and downward by the contrary powers, such that half of the powers push the nodes of the corrugations tending upward; but the remaining half pushes the curvatures tending downward.

These things being premised