NIPHER OUTPUT OP^ THE NON-CONDENSING STEAM ENGINE. 443 



tive pressure would continually fall as represented by the hyper- 

 bola. The part of the curve corresponding to negative values of 

 n has no physical significance. The engine when brought to 

 rest with any fixed load tc, by a decrease of boiler pressure, 

 would not reverse if the boiler pressure were still more reduced, 

 until it became less than the atmospheric pressure. 



2 - R'^ln 

 Multiplying (21) by 



1 J to \ /J 33OCO 



33000 \ ^ k^P,^E{jb^c)n] ^ ^ 



This equation corresponds to (lo). 



The condition of maximum /HI' for constant P' is 



This like (ii) is the equation of a parabola. The value of n is 



h^P j^E ^ I I (/, + />,+Jg) ( /,4-P„)(>i4 -P^) . 

 " = 3+^ ^ ^^cV /. ^-^^ 



The slope of this parabola is 



which when n = o \s 

 (dr'-] 7. 



while the line of zero load has the equation 



/, + /"= ^' \/^+P^-^B+(5 + c)n] . . . (27) 



« ~r -* L J 



as is readily determined from (22). 



The writer has examined engines in which the friction pressure 

 increases with the pressure of the supply steam at constant load* 

 The value of P^ then becomes PQ-\-en, and the surface of brake 

 horse-power as a function of mean effective pressure is then 

 represented by equations similar to that which in this paper 



