225 



tion.'^ This is so obviously an abuse of language tliat it needs 

 no further comment. 



21. Mr. S. Baring-Gouldj in a very unsuccessful attempt to 

 elucidate dynamical principles,"^ has defined force to be that 

 which produces or resists motion; and further on v/e meet with 

 confusion worse confounded, for not only light, colour, heat, 

 electricity," but ^Mimension . . . solidity, liquefaction, vapori- 

 sation," are modes or modifications of force: how colour" 

 and " dimension" are to produce or resist motion" it is not 

 easy to apprehend. An indefinite number of such misapplica- 

 tions of the term " force " might be further adduced, but 

 enough has been stated to show the very loose manner in which 

 that term has been used by writers on physical subjects. 



22. The terms force and energy are frequently used indis- 

 criminately in common parlance; "thus, it is common to 

 speak of the force of the powder, and the force of 

 the shot : the powder has force, but the shot only energy. 

 Again, the terms ' force of inertia,^ ' force of percussion,^ 

 ' centrifugal force,' have been frequently but erroneously em- 

 ployed. Inertia is simply the negation or non-existence of any 

 disturbing energy. In cases of percussion, the energy of the 

 striking body may be more or less imparted to the body struck, 

 either with or without the intervention of the force of elasticity. 

 This may be shown by means of two suspended ivory balls. If 

 a little bit of putty be placed on the point of impact of one ball 

 at rest, and the other be raised and allowed to impinge directly 

 upon it, they will swing together to half the height that the one 

 ball descended from, because the energy acquired by the 

 descending ball is just sufficient to raise double the mass to 

 half the height. But if the elasticity of the balls be allowed 

 to come into play by the removal of the yielding material, then 

 the striking ball remains at rest, and that which was struck 

 rises very nearly to the height from which the former descended, 

 elastic force having in this case imparted to the ball at rest nearly 

 the remaining half of the energy of the striking ball. The 

 instantaneous transmission of the energy of impact through a 

 long row of glass balls in contact may be adduced as a rough 

 illustration of the molecular transmission of energy : if the 

 first ball of the row be struck, visible motion will be imparted 

 to the last only. The term ' centrifugal force,'' denoting the 

 tendency of a revolving body to fly off from its orbit, will in 

 all cases be correctly replaced by ' centrifugal energy.^ " 



23. In order to maintain a logical accuracy of diction in treat- 

 ing the subject of this paper it becomes necessary to consider 



^ Origin and Development of Beligious Beliefs Part I., chap. I. 



