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and as such are radii of the circle to whose centre they are attached, 

 and whatever is true respecting one of them must be equally true 

 respecting the other. If, therefore, the rod AB rotate on its 

 axis C during the orbital revolution, the rod DE must, by parity 

 of reasoning, rotate on its own axis c. At the same time both 

 rods together rotate, as radii of the circle, round the centre of 

 the circle; so that each of them, during a complete orbital revo- 

 lution of their respective axes, performs three distinct revolutions 

 round about no less than three distinct centres all at once : AB 

 turns round, 1^^, the common centre ; 2d, its own axis C ; and, 

 Zdy DE's axis c ; while DE also turns round, Ist, the common 

 centre ; 2d, it own axis c ; and, 3d, AB's axis C. The same 

 thing must happen with every pair of opposite spokes in every 

 wheel: each spoke is the radius of a circle, attached to the centre 

 like AB ; and if AB rotate on its own centre of gravity at the 

 circumference of the circle, so must each spoke, placed as it is 

 in precisely the same circumstances, revolve round its own centre 

 of gravity, and, with the help of its opposite neighbour, perform 

 three circular revolutions, round three different axes, where no 

 human eye can see, and no human understanding can discover the 

 possibility of more than one, namely, that round the axle of the 

 wheel, the common centre of all the radii. Again, if AB turn round 

 on its own centre C, each half of AB divided by C will also, in 

 each rotation of the rod round C, turn round on its own 

 centre of gravity, and so on, as far as matter is divisible; so that 

 in every case of a body's revolving on an axis, we should have 

 an infinite multitude of wheels within wheels, all revolving and 

 rotating at once ; but which will be all swept away at once, like 

 the Ptolemaic cycles and epicycles, by means of the simple truth, 

 that in the case of the rod AB and of all bodies similarly situ- 

 ate, as the diameters and radii of wheels, moons, and planets, 

 there is and can be only one revolution round otie centre, namely 

 the centre of the orbit, so long as the same point of the rod, the 

 same end of the diameter, or the same point of circumference of 

 the revolving body remains in one with its radius-vector and the 

 centre of the circle. 



But, say mechanicians and astronomers, if the rod AB were 

 not to rotate on its axis, its point A would move away from the 

 centre, and all its parts, in length, would remain perfectly pa- 

 rallel to the straight line NS of our first experiment on the 

 wall. To be sure it would, but the nature, the cause, and the 

 result of such a movement and such a parallelism have been 

 abundantly shown already. Such a movement of the point A 

 from the centre would be an act of rotation round its own axis 

 C. Moreover, such a rod as AB has no inherent power of 

 rotation to bring its points back to the radius-vector ; therefore 



