REVIEW OF FEED- WATER TESTS. 273 



veloped 56 horse-power less than the H. P. cylinder when the 

 re-heater was off, and 19 horse-power less when the re-heater 

 was on. 



The effect of the jacketing and re-heating is also seen to 

 be very marked when comparison is made between the steam 

 accounted for in the two cylinders. In Engine No. 47, with 

 the jackets off, the steam accounted for in the L. P. cylinder 

 at cut-off is 10.8% less than in the H. P. cylinder; whereas 

 with the jackets on, the difference is only 1%. In Engine 

 No. 52, with jackets off, the steam accounted for in the L. P. 

 cylinder is 8.4% less than in the H. P. cylinder. When 

 the jackets were on, it was 12.9% more than in the H. P. 

 cylinder. In Engine No. 48, the steam accounted for in 

 the L. P. cylinder with the re-heater off, was 11.6% less 

 than that in the H. P. cylinder; whereas, when the re-heater 

 was on, it was only 4.2% less. In Engine No. 55 the effect 

 of the re-heater on the diagrams is seen to be considerable, 

 from the fact that the steam accounted for in the L. P. 

 cylinder is 1.3% more than that accounted for in the H. P. 

 cylinder. 



VIII. EFFECT OF RATIO OF CYLINDER AREAS IN 

 COMPOUND ENGINES. 



In most of the compound engines given, where these are of 

 the Corliss or other 4- valve type, the ratio of cylinder areas is 

 between 3.5 and 4. Three cases are given, however, where 

 the ratio is about 7 to 1, these being Engines 47, 51, and 52. 

 The engines with the large ratio of cylinder area show more 

 economical results than the others. The difference is not so 

 noticeable in No. 52 as it is in Nos. 47 and 51. In both these 

 cases, however, the pressure is higher than it is in most of the 

 tests given with the lower ratios ; and this higher pressure fur- 

 nishes one reason for the better result. There is one case of a 

 pressure of 151 Ibs. in an engine having a low ratio with which 

 these may be compared, and that is Engine No. 55. This 

 engine gives a horse-power for 13.27 Ibs. of feed- water per 



