388 Mr. W. J. Macquokn Rankine on the Science of Energetics. 



Effort, or Active Accident. 



The term "effort^' will be applied to every cause which varies, or 

 tends to vary, an accident. This term, therefore, comprehends not merely 

 forces or pressures, to which it is usually applied, but all causes of varia- 

 tion in the condition of substances. 



Efforts may be homogeneous or heterogeneous. 



Homogeneous efforts are compared by balancing them against each 

 other. 



An effort, being a condition of the parts of a substance, or a relation 

 between substances, is itself an accident, and may be distinguished as an 

 "active accident.'^ 



With reference to a given limited substance, internal efforts are those 

 which consist in actions amongst its parts ; external efforts those which 

 consist in actions between the given substance and other substances. 



Passive Accident. 



The condition which an effort tends to vary may be called a '^passive 

 accident," and when the word "accident" is not otherwise qualified, 

 "passive accident" may be understood. 



Radical Accident. 



If there be a quantity such that it expresses at once the magnitude of 

 the passive accident caused by a given effort, and the magnitude of the 

 active accident or effort itself, let the condition denoted by that quantity 

 be called a '■^radical accident." 



[The velocity of a given mass is an example of a radical accident, for 

 it is itself a passive accident, and also the measure of the kind of effort 

 called accelerative force, which acting for unity of time, is capable of 

 producing that passive accident.] 



[The strength of an electric current is also a radical accident.] 



Effort as a Measure of Mass. 



Masses, whether homogeneous or heterogeneous, may be compared 

 by means of the efforts required to produce in them variations of some 

 particular accident. The accident conventionally employed for this pur- 

 pose is velocity. 



Work. 



" Work " is the variation of an accident by an effort, and is a term 

 comprehending all phenomena in which physical change takes place. 

 Quantity oftvork is measured by the product of the variation of the 

 passive accident by the magnitude of the effort, when this is constant ; 



