Unpublished abstract, 'On the law of the variation of the flexibility of Canadian fir' by Charles Dupin Abstract in English of Dupin's paper written in French in which he attempts to produce a mathematical law governing the variation in flexibility of timber from the root of the tree to the top, with the timber from the root being the strongest. Corrections and deletions appear throughout in ink. Subject: Botany / Mathematics Communciated by Sir Joseph Banks. Read to the Royal Society on 16 March 1820. [1820]