120 



Professor H. S. HeU-Shaw 



[March •»!, 



We therefore now know that the limit of speed is controlled by- 

 two factors : — 



(1) Physical endurance, owing to the expenditure of work occur- 

 ring at an increasing rate as the speed is increased. 



(2) The physical impossibility of giving a reciprocating move- 

 ment to the legs quicker than a certain limited period of time. 



10 20 K) 40 50 60 70 80 90 IOC 



MILES 



Fig. 2. — Speed Records for Human Muscular Effort. 



I have prepared a chart, Fig. 2, which shows the maximum 

 recorded velocities of man's progression in walking and running. 

 The speeds are set up as vertical ordinates, and the abscissse represent 

 the distances over w^hich the respective speeds were maintained. It 

 will be seen that the maximum speed of walking is about 9 miles an 

 hour for a short distance, but when the long distance of 100 miles 

 is covered, the quickest rate recorded falls to 5^ miles an hour. For 

 running, the quickest speed which I have mentioned, viz. 21| miles 



