7 On Petty's return to England, probably through the influence of Hobbes, he was introduced to Hartlib. This remarkable man, whose name is familiar in the literary history of the time (cf. Masson's "Life of Milton"), became Petty's patron. In a letter to Boyle of 1647 (Boyle's Works, vi, 77) he expresses great admiration for the talents of his young acquaintance.
I put into your hands the design of the history of trade. The author is one Petty, twenty-four years of age, a perfect Frenchman, and a good linguist in other vulgar languages, a most exact anatomist, and excellent in all mathematical and mechanical learning. As for solid judgment and industry altogether masculine.
Petty soon became interested in Hartlib's scheme for the reform of education, and showed his desire to co-operate in the movement by writing a "Tractate on Education," dedicated to Hartlib. At the same time he invented a copying machine. Reference is made to this invention in the "Tractate." A parliamentary patent[1] was secured for it, and a description of it, dedicated to Robert Boyle, was printed in 1648.[2] This invention, like a good many of Petty's later mechanical devices, proved a failure. Curiously we find in a letter, written by Sir Christopher Wren some years after, a reference to a similar machine.[3] Wren, without mentioning any name, complained that a model of his invention, in a still imperfect condition, had been seen by chance by a visitor, and reproduced. The failure of the reproduction of his unfinished invention had made it impossible for him to give to the world his own perfected instrument for multiplying copies of writing. The history of Petty's
