FORCE, ENERGY, AND WILL. 



ONE benefit due to the advance of physical science is, as 

 Professor Clerk Maxwell has remarked, the introduc- 

 tion into common speech of words and phrases consistent 

 with true ideas about nature instead of others implying false 

 ideas. But though our scientific progress has produced this 

 amongst so many other beneficent effects, yet, as its advancmg 

 stream has left here and there a stagnant pool, so we ma}' 

 not unreasonably expect every now and then to meet even 

 with a temporary verbal backwater. Thus electrical discovery 

 by the term ' electric fluid ' has left in the popular mind the 

 illusion that electricity is a fluid substance which flows from 

 one body to another. But a really grave misconception (in 

 some respects a retrograde error) appears to me to be coming 

 daily more diffused with regard to the conceptions ' energy ' 

 and ' force.' 



The term ' force ' has, of course, definite and exact mean- 

 ings ^ (not always quite consistent, however,) assigned to it in 



1 Thus Professor Tait, in his Lectures on Some Recent Advances in Physical. 

 Science^ defines (at page 16) 'force' as 'any cause which alters or tends to 

 alter a body's natural state of rest or of uniform motion in a straight line.' 

 At page 354 he says : ' Force is the rate of change of momentum,' and adds 

 that the term ' is obviously to be applied to any pull, push, pressure, tension, 

 attraction or repulsion, etc. , whether applied by a stick or a string, a chain 

 or a girder, or by means of an invisible medium such as that whose existence 

 is made certain by the phenomena of light and radiant heat. ' At page 358 

 he adds : ' Force is the rate at which an agent does work per unit of length.' 

 In Nature, July 5, 1877, he tells us : 'In all probability there is no such thing 

 as force. ' Force is often taken to denote ' the unknown cause of energy, ' 

 ' energy being the power possessed by a body of overcoming a resistance. ' 

 Force is also defined as ' mass animated by velocity, or directed pressure. ' 



