  Gassendi's mechanics shows the strong influence of the Galilean programme. He addresses the law of free-fall twice, first in a faulty treatment in De Motu (1642), and next in corrected fashion in De proportione qua gravia decidentia accelerantur (1646). In the earlier work, Gassendi focuses on forces compelling the falling body, which he takes to comprise the attractive force of magnetism and the propelling force of air behind the falling body. This combination of forces, he suggests, allows for the Galilean law that the distance traveled by bodies in free-fall is proportional to the time of fall squared. However, Gassendi mistakenly takes increases in velocity and in distances to be equivalent, leading him to manufacture a false need for greater velocity attained than what would be produced by the attractive forces alone. In De Proportione, he acknowledges this error, amends his calculations, and retreats to a causal account that rests on the single force of the terrestrial magnetic attraction. This is not one of Gassendi's empirical triumphs, though—in neither work does he make any specific reference to observations or experiments.