4S8 Prof. Clausius on the Application of the Mechanical 



58, The quantities of work in this Table, as well as those in 

 the former Table for machines without condensers, refer to a 

 kilogramme of vapour coming from the boiler. It is easy, 

 however, to refer the work to a unit of heat furnished by the 

 source of heat ; for eveiy kilogramme of vapour requires as 

 much heat as is necessary, first to raise the mass / (somewhat 

 more than one kilogramme) from the temperature it had when 

 entering the boiler up to the general temperature of the same, 

 and then at that temperature to convert a kilogramme of it into 

 vapour. This quantity of heat can be calculated from former 



59. In conclusion, I will add a few remarks on friction, re- 

 stricting myself, however, to a justification of my having hitherto 

 disregarded friction in the developed equations, by showing that 

 instead of introducing the same at once into the first general 

 expressions for the work, as Pambour has done, it may also, ac- 

 cording to the same principles, and according to the manner of 

 other authors, be afterwards brought into calculation. 



The forces which the machine has to overcome during its 

 action may be thus distinguished : — (1) The resistance exter- 

 nally opposed to it, and in overcoming which it performs the 

 required useful work. Pambour calls this resistance the charge 

 of the machine, (2) The resistances which have their source in 

 the machine itself, so that the work expended in overcoming 

 them is not externally of use. All these resistances are included 

 in the term friction ; although, besides friction in its more limited 

 sense, they comprise other forces, particularly the resistances 

 caused by pumps belonging to the machine, exclusive of the one 

 which feeds the boiler, and which has already been considered. 



Pambour brings both these kinds of resistances into calcula- 

 tion as forces opposing the motion of the piston ; and in order 

 conveniently to combine them with the pressures of the vapour 

 on both sides of the piston, he also adopts a notation similar to 

 the one ordinarily used for vapour pressures ; that is to say, the 



