99 



entail a certain amount of repetition^ but the complexity of the 

 subject seems to render it almost inevitable."^ 



3. The vagueness in the use of the term "force^^ is acknowledged 

 by Dr. Tyndall in these words : — " But ambiguity in the use of the 

 term 'force^ has been for some time more and more creeping 

 upon us. We called the attraction of gravity a force without 

 any reference to motion. We applied the term ' force ' also to 

 that molecular attraction which we called ' chemical affinity/ 

 When^ however, we spoke of the conservation of force in the 

 case of elastic collision, we meant neither a pull nor a push, 

 which, as just indicated, might be exerted upon inert matter, 

 but w^e meant the moving force, if I may use the term, of the 

 colliding masses.^^ Force is here, consequently, applied in two 

 wholly different senses, so that the reasoning applicable to it in 

 the former sense would not be applicable to it in the latter. His 

 general usage of the word, however, indicates that he considers 

 it as energy, or working power j he is at liberty to use it as 

 equivalent to energy, if he wishes ; but not at the same time to 

 use it without any reference to motion whatever. 



4. Mr. Justice Grove is more satisfactory when he states that 

 "the term Force, although used in very different senses by dif- 

 ferent authors, in its limited sense may be defined as that which 

 produces or resists Motion.'^ Again he says, "I therefore use the 

 term Force, as meaning that active principle inseparable from 

 matter which is supposed to induce its various changes.^' He 

 here distinctly allows that matter invariably possesses a power 

 of producing or resisting motion, which power he names Force. 

 If this power be "inseparable from matter, it cannot be trans- 

 ferred from one atom of matter to another; motion may be 

 transferred, but not the power to produce the motion; that 

 must remain invariably an attribute of all matter, according to 

 his own acknowledgment. Yet we find him writing in a previous 

 paragraph that it is an " irresistible inference from observed 

 phenomena that a force cannot originate otherwise than by 

 devolution from some pre-existing force or forces." If he 

 mean by this that material powers are not self-originated, but 

 are the result of volitional power or powers, he is consistent with 

 himself, and states what we believe to be a fact ; but if he mean 

 that material powers in exercise are, necessarily in all cases, the 

 devolution of pre-existing material powers, he is contradictory, 

 because if matter can devolve this power to other matter, it is 



* This subject has been treated in the London Quarterly Review for July, 

 1871, by the Rev. J. Moore, with his usual well-known ability, in an article 

 on " The Heresies of Science," which ought to be earnestly studied by all 

 who value Logic more than " Imagination " in Science. 



