92 ENGINE TESTS. 



percentage of moisture varied from to 1 per cent. The 

 steam valves were fairly tight. The piston and exhaust 

 valves of one cylinder were absolutely tight. Those of the 

 other cylinder leaked a trifle. The load consisted of cotton 

 machinery. 



Two tests were made, one with both cylinders in operation 

 and the other with a single cylinder, and in both the load was 

 practically the same. The tests were made with different 

 boiler pressures. 



In this case it appears that the economy of feed-water con- 

 sumption was practically the same whether one cylinder was 

 used or the whole engine. As would be expected, however, 

 the proportion of steam accounted for by the indicator was the 

 least in the case of the earlier expansion. 



In a series of experiments, of which these formed a part, a 

 test was made to determine the effect of increasing the boiler 

 pressure 20 Ibs. above the normal, one cylinder being in use. 

 In one case the pressure was 85.8 Ibs., and in the other 105.7 ; 

 and the mean effective pressure was, in round numbers, 41 Ibs. 

 in both cases. The cut-off occurred at T y^ of the stroke in 

 one, and T ^\ of the stroke in the other. The steam consump- 

 tion with the high pressure was 19.5 Ibs. per I. H. P. per hour, 

 and with the low pressure 19.2. In other words, there was a 

 trifling loss due to the increase of pressure. This engine was 

 not absolutely tight, and doubtless leakage affected the results, 

 so that the advantage of the increase of pressure was to some 

 extent counteracted. 



On the last mentioned test the steam accounted for was .67. 



