24 THE REASON WHY : 



" Leisure is pain ; takes off our chariot wheels ; 

 How heavily we drag the load of life; 

 Blest leisure is our curse." YOUNO. 



through it, draw one string: in each hand, B, B, not towards you in the \ir%' A, C- 

 but sideways, till hoth strings are stretched in a straight line : you will see how 

 much swifter the stone moves than it did before when pulled straight forward. Not* 

 this is proved by mathematical reasoning to be the necessary consequence of iorces 

 applied obliquely ; there is a loss of power but a great increase of velocity. The 

 velocity is the quality required to be gained. 



63. By what mechanism are the motions of the arm performed ? 

 The arm is joined to the body, and moved by numerous powerful 



muscles ; and is fixed to the breast by the ligaments of the collar-bone. 

 The muscles that move the shoulder-blade lie upon the trunk ; those 

 that move the arm lie upon the shoulder-blade ; those that move the 

 fore-arm lie upon the arm ; and those that move the hand and 

 fingers lie upon the fore-arm. But as the arm requires easy, circular 

 motions, it has a multiplicity of parts to perform them. It has the 

 wrist, for turning it round ; the elbow, for its hinge-like motions ; 

 and the shoulder-joint, on which it rolls ; and to assist all those, the 

 moveable shoulder-blade becomes the centre of their motions ; for, 

 after a certain point of elevation, the motion of raising the arm is 

 performe J by the action of the shoulder-blade upon the trunk ; 

 when cur shoulder-bone is raised to a horizontal position, it is 

 checked by the upper part of the shoulder-joint which hangs over 

 it -, and if we elevate our arm still higher, the shoulder-blade rolls, 

 turning upon the point of the collar-bone ; and, as it turns, it glides 

 easily upon those muscles, which lie like a fleshy cushion between 

 it and the trunk over which it is placed. 



64. Why are the muscles often removed by means of slender strings 

 from the parts they are designed to rest upon ? 



Because, in many cases, the situation of the muscles where they 

 are immediately required would be inconvenient. If the muscles 

 which move the fingers had been plaoed in the palm or the back of 

 the hand, they would have swelled that part to an awkward and 

 clumsy thickness ; the beauty and the proportion of the part 

 would have been destroyed. They are, therefore, disposed in the 

 arm, and even up to the elbow, and act by long tendons strapped 

 down at the wrist, and passing under the ligaments to the fingers 

 %nd to the joints of the fingers which they are severally to 



