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volution is just as impossible as it would be for a cannon ball to fly 

 from earth to heaven, and again from heaven to earth and round 

 about the stars, without moving from the r/un. The earth never 

 quits its position in, or near to, the centre of the moon's orbit ; the 

 radius-vector merely represents a certain point of the earth's cir- 

 cumference considered as expanded to the size of the orbit ; and 

 a certain point of the moon's circumference remains continually 

 attached to the radius ; how, then, is it possible, in the nature of 

 things, that they can revolve round about a body, or point, or per- 

 son that not only remains, as the moon's centre always certainly 

 does, at a distance from, and to the outside of, the circle described 

 by her inner point of circumference ; but is also continually in 

 motion round about the very objects — the earth, the radius, and 

 the moon's attached point, that are said to revolve about it ? The 

 earth revolves about the moon's centre, but without leaving its 

 fixed place, in the centre of the moorHs orbit, at the very time the 

 moon's centre is revolving about the earth. This is just the rod 

 AB in one of its worst phases ; and the very error committed 

 by Galileo, when he thought he must have gone round about the 

 water if, as he inferred, the water had not turned round on its 

 axis. The earth, considered relatively to the moon, moves not at 

 all ; the nearest point of the moon, in one with the radius- vector, 

 describes an orbit of 1,434,000 miles ; while her centre, a thou- 

 sand miles farther from the earth, describes an orbit 6000 

 miles larger, yet do both the earth, which never moves, and 

 the moon's point which describes the smaller orbit, perform a 

 revolution round about the point ivhich describes the larger orbit, 

 and which consequently remains invariably on the outside of them. 

 How the earth, represented by the point A, and the radius- vector, re- 

 presented by the body of the rod AB, could revolve about the moon's 

 centre C, without the earth forsaking her fixed central position and 

 crossing the moon's orbit twice, in going to the outside and re- 

 turning, in the course of her circumgyration, far transcends my 

 comprehension ; and, were it not that such men as Galileo and 

 Laplace have said it, I should scarcely have believed it possible 

 for any human being to deliberately sanction and promulgate 

 an opinion that seems so preposterous. 



Laplace proceeds to say : *' If the moon were without a motion 

 of rotation, her radius- vector would trace, at every lunar revo- 

 lution, the circumference of a great circle upon her surface, every 

 point of which would be successively turned to us." I have 

 shown already that this is impossible, and need not repeat my ar- 

 guments and illustrations here. But, either he or his translator 

 " brings" the absurdity to a climax when he says : '* At the 

 same time that the radius-vector traces this circumference, the 

 lunar globe by its revolution brings always very nearly the same 



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