EN-ERG Y AND ITS TRANSFORMATIONS. 



or modifying energy, whatever the kind of force, what- 

 ever the kind of matter : it thus covers the whole 

 range of chemistry and physics. 



Matter is that which is capable of directly affecting 

 the senses, and which occupies space. Nothing is 

 known of the ultimate nature of matter, and we are 

 acquainted with it only as it affects the organs of the 

 body. It is usually divided into four classes : solids, 

 liquids, gases, and imponderable matter ; the latter 

 meaning that which cannot be assigned a finite specific 

 measure of mass or weight. The luminiferous ether is 

 an example of this last ; the other three are familiar 

 forms. 



A Body is a limited portion of matter. 



Force is that which produces, or tends to produce, 

 motion, or change of motion, in bodies ; it is measured 

 statically by the weight which will counterpoise it or 

 by comparison with a known standard of force, and 

 dynamically by the velocity which it will give a known 

 freely moving mass in a stated time, i.e., by the ''ac- 

 celeration " which it is capable of producing. 



Work is always performed by the expenditure of 

 energy, and is the product of the resistance overcome 

 by a force, or of the effort exerted by it, into the space 

 through which that action takes place. That resistance 

 may be constant, or variable, and due to an active, oppos- 

 ing force, to resisting pressure, to the inertia of masses, 

 or of molecules compelled to submit to acceleration or 

 retardation ; or it may be due to any one of the phys- 

 ical or chemical forces. Thus, if U represents the work 

 done by a force, acting through a space, s. 



U=Fs^Rs\ 



(I) 



