The manner in which the construction and general arrangement of the driving mechanism, the road surface, and other conditions control the application of power is a curious study. In connection with it I have made an instrument to illustrate the same graphically, which, for the sake of a name, we will call the “Cyclograph,” an engraving of which will be found below. [Illustration: The Cyclograph.] A frame, _A A_, is provided with means to attach it to the pedal of any machine. A table, _B_, supported by springs, _E_, _E_, has a vertical movement through the frame _A A_, and carries a marker, _C_. The frame carries a drum, _D_, containing within it mechanism which causes it to revolve regularly upon its axis. The cylindrical surface of this drum, _D_, is wrapped with a slip of registering paper removable at will. When we wish to take the total foot-pressure, the cyclograph is placed upon the pedal and the foot upon the table. The drum having been wound and supplied with the registering slip, and the marker _C_ with a pencil bearing against the slip, we are ready to throw the trigger and start the drum, by means of a string attached to the trigger, which is held by the rider so that he can start the apparatus at just such time as he desires a record of the pressure. The following are a few sample sections cut from registering slips illustrating some of the points discovered in these experiments. Only a few strokes of the crank or lever can be shown; it is evident that great space and expense of reproduction would be required to give the entire record for even a small part of a mile. It will be understood, I think, without further explanation, that these curves show the extent and variation of pressure of the foot upon the pedal in order to drive the respective machines under circumstances named and described by the figures and thereafter. [Illustration: 52-inch Ordinary; race-track; getting up steam.] [Illustration: 52-inch Ordinary; race-track; speed, eighteen miles per hour.] [Illustration: 52-inch Ordinary; race-track; speed, ten miles per hour.] [Illustration: 52-inch Ordinary; race-track; speed, ten miles per hour.] [Illustration: 52-inch Ordinary; up hill, grade, one foot in twenty-five; speed, about eight miles per hour.] [Illustration: 52-inch Ordinary; starting up hill.] [Illustration: 52-inch Ordinary; up hill, grade, one foot in ten; stalled at four miles per hour.] [Illustration: 52-inch Ordinary; up hill, grade, one foot in twenty-five; curves of both pedals superposed.] [Illustration: 52-inch Ordinary; back pedal; down hill, grade, one foot in twelve.] [Illustration: Rear-driver Rover type, 54-gear; up hill, grade, one foot in twenty; speed, nine miles per hour.] [Illustration: Rear-driver Rover type, 54-gear; up hill, grade, one foot in twenty; continuation of No. 10.] [Illustration: Rear-driver Rover type, 54-gear; up hill, grade, one foot in seven; speed, ten miles per hour.]