 According to Kilvington, in order to characterize changes in the speed of motion, one must analyze the problem of local motion in its kinematic aspect, which takes into account distance traversed and time consumed. He correctly recognizes that to measure the speed of motion that lasts some time, it is enough to establish relations between time and distance traversed. In his opinion, the same distances traversed in equal intervals of time characterize uniform motion. Uniformly difform motions are characterized respectively: accelerated motion by the same distance traversed in a shorter interval of time; decelerated motion by the same distance traversed in a longer time; or, according to modern definitions: the motion is uniformly difforme if the speed changes by equal amounts in equal intervals. Kilvington provides a proper description of free fall, noting that speed increases by the same amount in each time interval, and that speed is equally slower at the beginning of each interval than at the end of it. Difformly difform motion is characterized by unequal distances traversed in unequal intervals of time; the speed of such motion changes unequally (see Jung-Palczewska 2002b).