VOL. XLI.] PHILOSOPHICAL TRANSACTIONS. SIQ 



What seemed the most probable sohition, was this : when the arm is ex- 

 tended, the posture being uneasy, there must be a re-action of the muscles, or 

 a continual pulling of the arm towards the body. When therefore the right 

 arm is made use of, the pulling will be from right to left; and consequently 

 the motion produced in the body held by it in the same direction, or from west 

 to east. When the left arm is made use of, the re-action of the muscles will 

 be from left to right, and therefore the motion of the pendulous body from 

 east to west. And, agreeably to this, he has observed, when he used his left 

 hand, all other circumstances continuing the same, the motion of the pendu- 

 lous body was from left to right, or from east to west, contrary to what was 

 observed when held by the right hand. Yet still neither of these solutions 

 would account for the variety of odd particulars he has met with under various 

 circumstances. 



He proceeded therefore to try with rests for his arm of different heights, 

 having an arm of wood, about 2 feet long, fixed to a rest for his telescopes, 

 which could be raised to any height wanted ; and then the experiment succeeds 

 only well, when the rest was lower than the electric area, and the arm was sup- 

 ported on its elbow, which was the posture constantly made use of, when 

 rested on a chair, the chair being lower than the electric area, that it might 

 less affect the effluvia, as was then thought. 



He began now to think, whether it was not possible, that an inclination to 

 a motion one way in the person that holds the body, might not have such an 

 influence on the arm, and consequently the string and pendulous body, as to 

 determine them the same way by some pressure or bias put upon it, though 

 no motion sensible, even to himself, was produced in the hand. If so, he 

 might, by a contrary inclination, produce a motion the contrary way. Having 

 therefore a fine day, and the circular cake being well excited, he tried if he 

 could not produce a regular motion from east to west, about the ball in the 

 centre, having his hand supported, as usual, on the back of a chair. He 

 found he could produce a very regular one from east to west for many revolu- 

 tions, and change from one motion to another, without being sensible he 

 moved his hand at all. 



He then wet the ball and string, as in the experiment beforementioned, and 

 found he could tire himself with a motion either from east to west, or from 

 west to east, as he pleased, without giving any motion, that he could perceive, 

 to his hand or fingers. Hence many odd experiments that please, may, when 

 repeated, succeed. 



Since therefore the motion of the pendulous body, from a point undoubtedly 



