The Energy of Segmentation 29 1 



of the quantity of heat absorbed from the surroundings at the 

 higher temperature, and the two temperatures involved.^ 



This equation is, now, a general expression of the apphcation, 

 to reversible cychcal processes such as the above, of the Second 

 Law, which demands in this case that the same quantity of work 

 be produced from a definite amount of heat by any reversible 

 cyclical process whatever, taking place at the same two tempera- 

 tures. It means that the maximum amount of work which, with 

 the help of any system which is itself not permanently modified 

 by the change, can be done by a definite amount of heat energy, 

 Qi at any definite temperature Tj, is directly proportional to the 

 difference between that temperature and any lower temperature with 

 which the system can be brought into communication. Accordingly 



may be called the "economic coefficient." 



The principle expressed by equation [3] is of great importance 

 both in general and for this present paper in particular; by means 

 of it there can be determined the effect of temperature on the 

 equilibrium conditions of a system, or on the value of the intensity 

 factor of any energy form that may be involved; or^ if some other 

 intensity be substituted for temperature, the effect of this could like- 

 wise be determined. 



Thus, if we consider a reversible change taking place in any 

 system whereby a quantity of heat Q, is taken from the surround- 

 ings at the temperature T, and a quantity of work ^ is produced 

 in them, and if the same change of state takes place in the opposite 

 direction and at a slightly different temperature, T + d T, and 

 thereby a quantity of work equal to — {W + dW) is produced in 

 the surroundings, there can be derived from equation [3], by sub- 

 stitution of the values: W,= W; W^= - {W + dW)\ Q, = Q; 

 r, = r;and T,= T+ dT"^ 



dw=^dr [4] 



'For the complete analysis and definition of this well-known equation, see Noyes, /J., pp. 148-153' 

 *For all the details of this, see Noyes, Id., pp. 156-159. 



