2 TlMEHRI. 



the condensed steam which took place in the high pres- 

 sure cylinder, it was enabled to do useful work in the 

 cylinder of lower pressure instead of passing dire6l to 

 the condenser. 



This is a digression which you will tolerate seeing the 

 analogy in the old difficulty of establishing a satisfa6lory 

 explanation of the behaviour of heat in Compound 

 Engines and our still existing want of a satisfa6lory ex- 

 planation of the behaviour of heat in multiple evaporators. 



Before proceeding further it is advisable to clearly 

 survey the ground we stand on, and state the beneficial 

 results we expe6l from the evolution of a satisfa6lory 

 theory. 



First. Taking the only true standard of efficiency ; 

 viz., work done for fuel used, there is no doubt whatever 

 that as much is being got out of the present cycle as is 

 possible, and that until a new cycle is introduced, (this 

 not probable), the most we can expe6l is improvement in 

 small details of constru6lion that will reduce the first cost 

 and upkeep of the apparatus ; but which cannot mate- 

 rially affe6l the economical work of a multiple evaporator 

 from a fuel point of view. 



Second. We can look for cheaper evaporators that 

 will require less to keep in order, by obtaining data that 

 will enable manufa6lurers to eliminate the deleterious 

 gases before they either monopolise a portion of useful 

 heating surface; or to damaging corrosion to the tubes 

 and pumps. 



With regard to the first clause ; we well recognise 

 that so long as Carnot'S principle is fulfilled in RiL- 

 LIEUX'S cycle, the amount of work done will depend on 

 the constant temperature at which heat is received and 



