As his notes began to take shape and he thought of printing them, it was natural for the inventive Leonardo to design his own printing press. It is one of the earliest such designs on record. Because the carrying bed which held the type and the paper was automatically adjusted to the handlebar, the press could be operated by one man. Besides his notes Leonardo also considered printing a work by Roger Bacon, the thirteenth century English scientist. This project for printing his own books, however, was never realized by Leonardo. Lately, he had received a commission which took him back in memory to the days of Ludovico. The subject was Marshal Gian Giacomo Trivulzio, a soldier-of-fortune. Originally this man was a loyal commander of Galeazzo Sforza’s but when Ludovico came to power he had had Trivulzio banished from Milan. Embittered, Trivulzio had become a stubborn enemy of Ludovico from that time on, serving under any banner that marched against the house of Sforza. A stocky, square-faced man, his body was covered with the scars of many battles. He had been fighting with the French ever since the time Ludovico had betrayed Charles VIII. Trivulzio had seen the great monument that Leonardo had modeled and, although it was riddled by French arrows and damaged by wind and rain, the Marshal was impressed and wished for a similar memorial to himself. Leonardo set to work immediately. His past experience with the Sforza monument was now to his advantage. This time there was no need for experimenting. He knew how much material he needed and the approximate cost of everything including the casting. He submitted an estimate of three thousand and forty—six ducats for the completed work, one hundred of which would go to Leonardo. The sum was acceptable to Trivulzio and Leonardo began his preliminary studies. As he gathered the material for this new equestrian statue, Leonardo and the French Viceroy Charles d’Amboise became interested in the further canalization of the plains of Lombardy. The use of canals and locks had been in practice for roughly a hundred years and around Milan there were already some fifty miles of canals and about twenty-five locks. Leonardo started another survey of the area. In his imagination, he envisioned a vast hydraulic engineering project. On September 12, 1508 Leonardo announced in his notes the beginning of a book on the nature of water. He had decided to separate this book from the one on hydraulics because it was necessary to separate theory and practice. His pages treating the science of hydraulics, or the practical applications of water power, had reached to “forty books of benefits.” By the spring of 1509 he had expanded his notes on the nature of water to include the greatest wave to the smallest raindrop.