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correct : Mutationem motus proportionaletn 

 esse vi motrici impressae, et fieri secimdum 

 lineara rectam qua vis ilia impremiter : name- 

 ly, that the mutation of motion, is always 

 proportionate to the force impressed, and is 

 always made according to that right line in 

 which that force is impressed." However true 

 it may be, that a given force impressed upon a 

 body, will give it a given motion, under the same 

 circumstances of external resistance, it must, 

 nevertheless, be acknowledged, that the same 

 force, impressed upon the same body, under 

 unequal degrees of external resistance, will not 

 excite on it the same degree of motion ;- the 

 same force acting on the same body, will pro- 

 duce a very different result, in a rare, to what 

 it does in a dense medium ; in air, to what 

 it does in water; in water, to what it does 

 when resisted by the solid nucleus of the 

 world, in which the resistance is so great, that 

 the same given force, acting upon the same 

 body, will produce no motion whatever. It is 

 the resistance which exists which not only tends 

 to change the direction of the force, by which a 

 body is moved, but to destroy motion altoge- 

 ther: the assertion, therefore, is not just, that 

 the mutation of motion is always proportionate 

 to the force impressed ; the mutation of motion 

 depends on the relation which exists between 

 the force, and the resistance which is opposed 

 by the body which is to be moved ; neither is 



