Amazon.com description: Product Description: Galileo’s enduring legacy was the establishment of mathematics as the basis for research in the physical sciences. The proving-ground for his methodology was the machine shop in his Padua home. There Galileo perfected the "geometrical and military compass" (or sector), a calculating ruler based on the principle of proportional magnitudes that brought speed and accuracy to computations about armaments and their trajectories. It was also widely used for complex calculations of proportion, volume, and square or cube roots well before the advent of logarithmic tables, the slide-rule, and the computer. Galileo’s book, the manual for his compass, was printed in an edition of sixty copies, and only a handful survive. This Octavo Edition includes complete images of the book and Stillman Drake’s authoritative English translation. Commentary by Filippo Camerota.