First edition of Galileo's final yet most important mathematical work, and a clean copy. The "two new sciences" were "the engineering science of strength of materials and the mathematical science of kinematics. The first, as Galileo presents it, is founded on the law of the lever; breaking strength is treated as a branch of statics. The second has its basis in the assumption of uniformity and simplicity in nature, complemented by certain dynamic assumptions" (DSB V, p.245).
As with his other major works, this is in the form of a dialogue between the characters Salviati, Sagredo and Simplicio, who had also appeared in his troublesome Dialogue concerning the two chief world systems of 1632. After Galileo's troubles with the papal authorities in Italy because of his earlier Dialogo, he had to publish this work abroad in a state where the ban on publishing his works was of little import.