268 



Essay on Motion and Force. 



reaching the earth. The tension remains unaltered until 

 some other change takes place ; the heat induces motion in 

 surrounding bodies and thus is merged into other modes 

 of motion, and so on, ad infinitum. 



Another term which is the offspring of erroneous notions 

 of motion and force, and which, I think, now seriously 

 retards the attainment of correct ideas upon this subject, 

 is inertia. 



I object to this term, because if it can be proper to con- 

 sider it as a property of matter at all, it is only a negative. 

 There would certainly be no end to the properties of 

 matter, if we should adopt the rule of calling negatives 

 properties. I might say of snow that it has the property of 

 not being black, of not being amorphous, and so forth, but 

 I should really not predicate any thing of snow by saying 

 this, and if in addition to this illogical language, it could 

 be proved that snow was really matter in an amorphous 

 condition, and that it was black, or if it yet remained to 

 be proved that such was not the case, the assertion would 

 not only be illogical, and thus calculated to mislead the 

 mind in thinking upon the subject snow, but would also 

 be either false or hypothetical. The idea conveyed by 

 the term inertia, is the want of power in matter to move 

 when at rest, or to come to rest when in motion. Silli- 

 man says: — "In consequence of inertia of matter if a 

 moving body should meet no resistance, it would continue 

 to move forever with the same velocity and in the 

 same direction." This idea would be correctly con- 

 veyed by saying that moving matter retains its motion, 

 until some change affecting the motion takes place, subse- 

 quent to the conditions which were the cause of its motion . 

 On the contrary it is asserted, that a body at rest will 

 remain at rest unless acted upon by some external force. 

 Here something is predicated of matter as existing in a 

 state of which we know absolutely nothing, rest ; and in 

 which state, we have every reason to believe, it does not 

 exist in the entire universe. Matter in a state of rest 



