ccxxxv 



Many of the evolutions performed upon it can be made equally well 

 upon swings of any length ; with others it is different. When the evolu- 

 tion is such that the swing in one direction marks a period of exertion, 

 while the return is comparatively a period of rest, then the evolution can- 

 not be equally well performed with swings of all lengths. 



One of the most useful exercises is made as follows : Reaching up and 

 grasping the rings, let the swing be started, and at the beginning of a for- 

 ward swing the feet are thrown above the head, the legs being fiexed. As 

 the forward swing closes, the legs are extended and the arms flexed, the 

 body being thus thrown upward and outward. Here, also, by some prac- 

 tice, one learns to accomplish the swing with a minimum of exertion, which 

 a good gymnast always does; nevertheless the number of swings, before 

 exhaustion takes place, varies with the length of the ropes, as is shown in 

 the following series of experiments made upon myself: 



NIPHER. 



/, distance from point of suspension to centre of hands; t, time of one complete oscill* 

 tion (forward and back); «, number of oscillations before exhaustion. 



It will be observed that n reaches a maximum where / = about 8.5 ft. 

 or where the time of a full swing is between 3.9 and 4.0 seconds. 



Another series of experiments was made upon Mr. Cunningham, a 

 young man about 5 feet 2 inches in height, and of light build. The maxi- 

 mum value of n is here reached when the length of the rope was about 

 10 feet, and here the time of a full swing was about 4.1 seconds. 



CUNNINGHAM. 



In order that this and similar evolutions may be elegantly performed, 

 the time for the full swing, when loaded with any person, should be four 

 seconds. 



The cause of rapid fatigue with long swings is, that the body must be 

 held in a constrained position for too long a time. With very short swings, 

 the muscles are forced to work with too great a velocity. 



