Opticks and The Principia
Opticks differs in many aspects from the Principia. First of all, it is written in English rather than Latin. Second, unlike the Principia, it is not presented in a strictly geometric form, with propositions proved by mathematics from either previous propositions or lemmas or first principles (or axioms). It does not prove its propositions by the use of ratios or equations, by the use of fluxions, or the tools of mathematics. Rather, the proofs generally proceed "by Experiments." In many ways, therefore, this work is a vade mecum of the experimenter's art, displaying in many examples the way to make experiments and to draw proper conclusions from them.
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