4 Reynolds, Dryness of Saturated Steam. 



of water passing with the steam into the engine, have 

 attracted a great deal of attention. 



For purely experimental purposes, it is always possible 

 to supply the engine with dry steam, even where the boiler 

 is at a distance, by passing the steam through a sufficiently 

 large vessel close to the engine, so that the water may be 

 disentangled by gravitation before the steam enters the 

 engine. These are called water-separators. In some 

 cases such separators form part of the engine, but, although 

 their employment is becoming more common, it is only in 

 comparatively few cases that this is practicable. 



In other cases, that is, in the great majority of cases, 

 the desire to obtain some experimental evidence of the 

 percentage of water in the steam as it enters the engine, 

 has led to the use of methods of testing samples of the 

 steam drawn continuously from the steam pipe close to the 

 engine. 



Sampling the Steam. 



In such methods, the question of getting a>fair sample of 

 the steam as it enters the engine is quite distinct from that 

 of testing the sample so obtained. The water in the pipe, 

 although moving in the direction of the steam, will not be 

 uniformly distributed throughout the steam, and will, to a 

 great extent, merely drift along the surface of the pipe and 

 mostly on the lower surface, so that unless a sample taken 

 from the lowest part of the pipe is found to be dry, in 

 which case the steam is dry, such methods afford but 

 little evidence as to the percentage of water entering the 

 engine with the steam. 



Testing the Samples. 



For absolute dryness such samples may, where the 

 pressure in the steam pipe is steady, be tested by allowing 

 the sample to flow quietly through a separator, so as to 

 drain out the water, the weight of which is then observed. 



