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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 we 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 ; he is at liberty to use it as 
equivalent to energy, if he wishes j 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 maybe 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 Eev. 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. 
