The introduction of resistance by means of the rheostat, R, was frequently a convenient method of correcting the chronoscope.
In a previous chapter I have described the "chronoscope" which was used by Marey.
Animal reacts and by its movements turns a key, RK (Fig. 6), thus making the chronoscope circuit and stopping the record.
As soon as the point touched the animal the chronoscope circuit was broken by the raising of the upper arm of the key.