50 Mr Henwood on the Expansive Action of Steam 



planks of some hard wood, which are always well covere'd with 

 grease ; they seldom fit very accurately. 



TABLE IV. — Duration of the Experiments, number of Strokes made. 

 Materials consumed, &;c. 



The engines were taken without any previous preparation, 

 and they were worked without intermission, at a speed just 

 sufficient to keep the mines clear from water ; but without 

 permitting the pumps to draw air (go in fork). The work- 

 men exercised their own discretion in the mode of working ; 

 for I purposely abstained from any other interference with 

 them than was sufficient to satisfy myself that every thing 

 was exposed to my notice, and fairly and honestly performed. 



The results will appear in 



TABLE V. 



* These numbers are on the assumption that each pump delivei's the full 

 computed quantity ; but in an experiment at Huel Towan, made by Sir 

 John Rennie and myself, the actual compared with the calculated delivery 

 was as 0.924 to unity. I have repeated the comparison at the same place, 

 with a similar result.' 



