PERIODIC COMETS. 



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Fig. 3. 





a \eryhigh tide, but a star of the same description, which, in its elliptic course 

 about the sun, directly struck the earth. Let us examine closely what would 

 be the effect of such an event. 



Let us conceive a solid body proceeding in a straight line with a certain ra- 

 pidity, and upon which from the outset another much smaller body had b<t-n 

 mertty placed. These two bodies, although not fastened together, will not sep- 

 arate in their progress, because the force which moves them will have gradu- 

 ally and from the commencement imparted equal velocities to them. But let 

 us suppose that an insurmountable obstacle suddenly presents itself in the way 

 of the first bod) and stops it instantly ; the fore part of the surface, the parts 

 struck, are, strictly speaking, the only parts whose velocity is directly destroyed 

 by the obstacle ; but as all the other parts are intimately attached to the first 

 as, from our hypothesis, ihe hotly is solid the whole of that body will stop. 



It will not be so with the small body which we have yitnply laid upon the 

 first. This we may stop without the other, to which nothing attaches it. un- 

 less it may be a slight degree of friction ; and it will experience no effect 

 lose none of its celerity. By virtue of this acquired and undiminished velocity, 

 the small body will separate itself from the large one, and will continue to 

 move in the original direction until the moment when its own weight shall 



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