On the Energy expended in Propelling a Bicycle. 313 
in addition to that caused by the scenery passed through and other collateral 
circumstances, arises also from the mere exercise, and with most riders is of some- 
what the same kind, but greater and more lasting than that experienced in riding 
on horseback. 
It is obvious to remark, that our experiments seem to show that an economy 
may be effected in workshops where human muscular power is employed, wherever 
it is possible to apply it in the same way as on the bicycle, and with the adjust- 
ments which the bycycle rider has at his disposal. It is plain from the experience 
of bicycle riders that most work can be done with a given expenditure of fatigue, 
when the pressure against which the feet move is much less than the whole weight 
of the body. 
Some information is given by plotting down on diagrams the results of all the 
experiments made on nearly level ground. This is done in Figures 9 and 10, PI. 
41, in which the points marked with a cross are those furnished by the experiments 
made in winter with the indicator apparatus attached to the top of the lever. 
Those representing the experiments made in summer, with the apparatus attached 
to the treadle, are surrounded by a circle. The scattered position of the points 
on these diagrams is, of course, owing to the great variety of conditions under 
which the observations were made—the state of the road, the wind, and the 
inclination (although always slight), having been very different. 
Nevertheless the curves drawn through the midst of these scattered points may 
be taken fairly to represent the average expenditure of energy in ordinary flat road 
riding to attainspeeds of from six to twelve milesan hour ; Figure 9, Pl. 41furnishing 
the energy which must be expended per mile, and Figure 10, Pl. 41 the energy per 
minute, or, in other words, the power which must be exerted. Both ot these rise 
rapidly with increasing speeds, and show that the lower speeds are much the most 
economical, 
It is of interest to inquire what is practically the most economical speed to adopt. 
This is found in practice to be the speed at which the machine will travel when 
the rider after lifting the rising leg does a little more than allow its 
weight to act on the descending pedal. Sauntering in this way is scarcely 
felt to be work at all, and is often the pace which is best suited to relieve the 
fatigues of sedentary occupations. This under the conditions of our experiments 
has been found to furnish a speed of nearly six miles an hour on an ordinary road 
without wind, and this experience agrees well with Figure 9, for taking the 
stroke as ten inches and the weight of the leg from the knee down, along with half 
the weight of the upper leg, to be seventeen pounds, we shall have fifteen foot- 
pounds of work done each stroke, or thirty each revolution of the wheel. This 
would assign 11,500 foot-pounds to the mile, which if we venture to extend the 
eurve in Figure 9, Pl. 41 backwards a very little, will bring it to a pommt which 
shows the corresponding speed to be five and three-quarter miles per hour. 
