Newton on wave theory. Book page showing text and a diagram illustrating a wave theory proposed by English physicist and mathematician Isaac Newton (1642-1727). This text (in Latin) accompanies a diagram showing a wave front diverging after passing through a hole. This early form of wave theory was the basis for Newton's attempt to calculate the speed of sound. This diagram was drawn for proposition 41, theorem 32, in section 8 ('Of motion propagated through fluids') from book 2 of Newton's 'Philosophiae Naturalis Principia Mathematica' (1686). The concluding QED (quod erat demonstrandum) signals Newton's demonstration of his proof.