274 ENGINE TESTS. 



hour. Engine No. 47 B gives 12.45 Ibs., while Engine Xo. 

 51 C, gives 11.89 Ibs. Taking the average of the last two, 

 which is 12.17, there is a difference between the two cases iri 

 favor of the larger ratio of areas of 1.1 Ibs. or S ( / f . Engine 

 No. 55, as will be seen, does not give so well-formed diagrams, 

 there being considerable wiredrawing in the H. P. cylinder; 

 and the result obtained on this engine is not so good as it 

 would have been if these conditions had been better. Making 

 due allowance for this, however, and further allowance for the 

 fact that Engine No. 51 was supplied with slightly superheated 

 steam, there appears to be a noticeable advantage in the use of 

 the higher ratio of cylinder area for an engine running at 150 

 Ibs. pressure. It is a noteworthy fact that with the high ratio 

 of area, an excellent steam distribution, and a slight amount of 

 superheating, the most economical result given in the whole list 

 of tests is produced,- Kn^ine No. 51 C producing a horse- 

 power for 11.89 Ibs. of feed-water per hour. 



IX. MISCELLANEOUS. 



The tests furnish some indication as to the loss of economy 

 produced by light loads, especially in non-condensing engines. 

 In Engine No. 10, which is a single-valve, sin^lr-acting engine 

 of the high-speed class, the consumption of steam per horse- 

 power per hour was increased I'nun -'2.J Ibs. to 36.27 Ibs., by 

 reducing the horse-power developed from 44.8 H. P. to 25.7 

 H. P. In Engine N>. 2-', which is of the single-valve high- 

 speed class, the consumption increased from 30.63 Ibs. to 31.78 

 Ibs., corresponding to a reduction of load from 39.4 H. P. to 

 22.2 H. P. In Engine No. 31, which is of the Corliss type, the 

 consumption was fairly constant with a load varying from 2:^2 

 H. P. to 342 H. P., but with lighter loads it rapidly fell off; 

 and with the load of the idle engine and shafting, which was 37 

 horse-power, the consumption rose to 73.63 Ibs. per I. H. P. per 

 hour. In Engine No. 42, which is a single-valve high-speed 

 compound, the consumption was increased from 25.2 Ibs. to 

 44.89 Ibs. by reducing the load from 152.5 H. P. to 45.6 H. P. 



