During this time Leonardo’s highly original mind was also at work on other devices. One of these was an _odometer_, an instrument for measuring the distance traversed by a vehicle. Dials, turned by a system of gears attached to the wheel of a wheelbarrow, measured the distance traveled as the barrow was pushed along the ground. In addition, Leonardo conceived a kind of odometer to be used at sea; this consisted essentially of a spinner that was towed by a ship which registered its speed. Leonardo even invented an automatic spit operated by metal vanes mounted in the chimney that revolved with the pressure of the hot air rising from the fire—and a pair of large floating shoes for walking on water! In the meantime, Charles VIII of France had marched through Rome and entered Naples. The conquest was without opposition. Charles was then crowned King of Naples and all Italy was at his feet. Yet his triumph was a short one. Ludovico, having used the king to get rid of his enemies, now plotted against the king himself. He formed an alliance with the Pope, Venice, Spain, and the German emperor. Charles, faced with this league, hastily beat a retreat to France. Fighting his way to the border, he there signed a peace treaty. Thus Ludovico had swept Italy clean of all opposition and was now the most powerful prince in the land. Yet Ludovico was quick to realize that his position could only be held by force and he set about strengthening himself and his allies. To provide for more cannons, a hundred and fifty thousand tons of bronze were sent to manufacturing works in Ferrara. This, however, included the very bronze Leonardo needed for the casting of his equestrian statue, and this is why the statue was never cast. Years of Leonardo’s work now seemed to vanish overnight. Ludovico also needed large sums of money to secure friends in high places and Leonardo’s own payments were suddenly dropped. Forced again to worry about paying for his daily bread and for his household and apprentices, he wrote letters to Ludovico complaining of his lack of funds and asking for money that was owed him for work done. He looked about for other commissions, but none were available. Moreover, because he was still court painter to Ludovico, he was ordered to paint the decorations of some rooms in the castle. But this was more than Leonardo could take—he walked off the job without finishing it.