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again to the right, in order to get round about the obstacle. In 

 making these shuffles, the opposite points of his own circumfe- 

 rence cross each other's paths ; because at every instant of pro- 

 gression the central axis of his body changes the direction of its 

 line of motion, without the points of his circumference turning 

 back in the same proportion, so as to occupy always their ori- 

 ginal places on the same side of the axis. This certainly does 

 not happen when he moves straight forward and backward ; and 

 these crossings of the different orbits described by the different 

 points of his own circumference are equivalent to, and precisely 

 effect, one complete rotation on his own axis. All the parts of 

 any horizontal section of his body move with the same velocity ; 

 and, to enable them to move through equal spaces in equal 

 times, they must find room for their movement by some going to 

 the outside, while others are falling back to the inside, of the or- 

 bit described by his perpendicular central axis ; and the reason 

 why he keeps his face always in the same direction, while he is 

 really rotating, is that what his circumference gains by rotation 

 in one direction is lost by his centre's moving forward in the op- 

 posite direction. Common sense might tell him this ; but the 

 string and the noose round his body confirm its dictates unde- 

 niably. The same would be the result of his shuffling along the 

 four sides successively of a square, or a parallelogram, or a 

 rhombus, with his face looking invariably in the same direction ; 

 north, or south, or east, or west, as the case might be. At each 

 of the four corners, all the points of his body cross each other's 

 paths horizontally: and, as before, these horizontal crossings 

 amount to one complete rotation round his perpendicular axis. 

 To make the experiment more complete, let him tie himself to 

 the centre of his circle by a slack cord, simply attached to a 

 button or button-hole of his vest, without a noose, and then 

 shuffle round, with his face always looking in the same direc- 

 tion. When he completes his revolution he will find the cord 

 drawn round about him. How could it get into such a position 

 unless he had turned himself round on his own axis, and drawn 

 it round along with that point of his outward man to which it 

 was attached ? It has not crept round about him of itself like 

 a living serpent ; yet has it been stretched out to the extent of 

 a whole circumference of the moving body ; a fact that, I pre- 

 sume, can only be accounted for by that body's having turned 

 round on its own axis, and drawn the cord round about with it. 

 Let him now, for a final experiment, just stop at any point of the 

 circle, with his face to the centre, and the cord attached, as be- 

 fore, to his button or button-hole, and turn himself once round 

 on his own axis, from east to w^est, or with his right shoulder 

 backwards. The cord will be drawn round about him, and this 



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