I have refrained from giving any tests as to the comparative power required to drive machines of the same type and of different manufacture, differences being liable to result from a bad condition of the machine, such as the want of oil, or from happening to get hold of an unusually bad sample, making the liability to do injustice too great. The writer does not feel himself called upon to judge of or express differences in quality of workmanship in general, if for no other reason than that by the time the matter goes to press, such merits or defects as he might have discovered may change. Workmanship does change, principles never can; and, what is more, the hypotheses and conclusions in regard to principles, treated of in this or any other book, are always open to contradiction; if injustice is done to any maker of wares in a matter of principle, said maker always has a remedy in defence, and if he can disprove assertions made his justification is complete, whereas if a mistake of fact is recorded, such as the operation of a certain machine, and the machine upon which the alleged fact is based happens to disappear, the party interested is denied a just remedy. There are of course certain criteria of good workmanship, and the same should be touched upon in order to teach the reader how to judge of it; but beyond this no writer should be allowed to go, unless at least he has been paid for advertising competing wares at regular rates. The cyclograph attached to the revolving pedal shows the total amount of pressure required to do a certain work on a machine; but if it is desired to ascertain the track resistance or the friction of parts alone, it is necessary to so place the instrument as to register the tangential resultant in turning the crank, taking no note of any power thrown away by indirect application; that is, if we wish to register the circular or tangential resultant, the cyclograph is attached by its frame rigidly to the crank or lever of a cycle, and the revolving pedal, which has been detached, is hung upon the spring platform. This last arrangement is used in experimenting to ascertain the extra power available by ankle-motion, as will be shown hereafter. ANKLE-MOTION AS SHOWN BY THE CYCLOGRAPH. Throughout this work a slight tendency to urge the element of dead centre as against the crank-cycle may have been discovered. Makers and riders who find fault with this apparent praise of lever and non-dead-centre devices can derive considerable comfort by the study of ankle-motion. No better introduction to our diagrams, showing the possibilities arising therefrom, can be given than the following extract from the _Irish Cyclist_, via _The Bicycling News and Wheelman’s Gazette_: “ANKLE-ACTION.