8 THE SCIENTIFIC PAPERS OF 



5. The condenser may be started and stopped at any time, by 

 turning the supply of injection water either on or off. If turned 

 on, it at once forms the vacuum, without involving the necessity 

 of blowing through ; and if turned off, it allows the engine to 

 proceed in the same manner as though no condenser had been 

 applied. 



6. The air contained in the condenser is at the commencement 

 of each stroke bodily expelled, which is of great advantage to the 

 formation of a good vacuum, instead of the ordinary air pump 

 removing only a portion of the air at each stroke, and consequently 

 leaving a portion always in the condenser. 



7. The regenerative condenser is more compact and even less 

 expensive than the ordinary injection condenser, being less than 

 one quarter of the size and having only one valve instead of three. 

 Its proportionate dimensions are as follows : Area of plate- 

 chamber, three times the area of exhaust pipe ; length of plates, 

 one-quarter to one-third of stroke of engine ; thickness of plates, 

 l-292nd part of their length ; spaces between plates, the same, 

 but never less than 1-1 6th inch, it having been found that the 

 alternate rush of water and condensing steam prevents the settle- 

 ment of grease and earthy matter between the plates, if they are 

 not less than 1-1 6th inch apart : capacity of displacing cylinder, 

 one and a half times the capacity of the plate -chamber. The 

 total capacity of the condenser is equal to only about one-tenth of 

 the capacity of the working cylinder. 



In applying the regenerative condenser to existing high-pres- 

 sure engines, a saving. of fuel of from 30 to '65 per cent, has been 

 effected, or an increase of power to that amount with the same 

 expenditure of fuel as previously. This saving may however be 

 still augmented considerably, if advantage be taken of the in- 

 creased effective pressure to work the engine expansively. In 

 most cases this may be easily effected, by merely adding to the 

 lap of the slide valve and increasing the lead of the eccentric 

 proportionately, whereby the additional advantage of a more 

 early discharge of the steam is obtained. 



The first regenerative condenser was attached to a 16-horse- 

 power high-pressure engine at Saltley "Works near Birmingham in 

 September, 1849, where it has been found to answer, although it 

 is not perfect in its proportions, and could not be kept constantly 



