This article discusses material from the doctoral thesis of Wilhlem Camerer, which was devoted to the topic of the timing of voluntary movements, and appeared in 1866, thus being one of the earliest studies of any aspect of time perception. It was conducted under the supervision of Karl von Vierordt, at the University of Tübingen in Germany. The data reported come from Camerer's attempts to make a movement over a distance of about 65 mm, either by flexion or extension of his arm, with the behavior recorded via a kymograph, and measured from its trace. Most of his data come from his attempts to make movements at a constant speed, with the speed varying from one trial to another from 5 to 60 mm/s, but he also conducted a study where the movement was intended to be accelerated or decelerated during the trial. In general, when extension movements were intended to be performed with constant speed, a gradual increase in movement speed usually occurred throughout the movement duration. For flexions the opposite occurred, albeit less clearly. Camerer linked the apparent distortions of speed to Vierordt's experiments on the perception of time and his thesis contains what is probably the first mention of Vierordt's Law, the proposition that short times are judged as longer, and long times as shorter, than they really are.
Keywords: Vierordt’s Law; acceleration; deceleration.