48 Mr Henwood on the Expansive Action of Steam 



Note to Table II. 

 The following are the dimensions of the heating surfaces of the boilers 

 of the three engines which were the principal subjects of my experiments. 

 I add those of Loam's engine, on the United Mines (with which I have 

 been favoured by William Francis, Esq., the scientific director of that 

 extensive mining establishment), as the only machine the evaporation in 

 which has been published. See Mr Lean's Report in the Cornwall Poly- 

 technic Society's Transactions, iv. (1836) p. 34. 



Loam's engine, at the United Mines, has the steam cylinder of eighty- 

 five inches in diameter, the stroke in it is ten feet, and in the pump 7.5 

 feet; the load is about 12 lb. per square inch of the area of the piston, 

 and the velocity about 4.8 strokes per minute : the elasticity of the steam 

 employed I am unable to state. From the 2d of March to the 5th of 

 August 1836, the duty was about sixty-five millions of pounds lifted ont- 

 foot, by 100 lb. of coal, and the evaporation by the same_ quantity of fuel 

 for the same period was 15.4 cubic feet. This is a sufficient approxima- 

 tion to the result which I had five years previously obtained at Huel 

 Towan. 



The stroke in the cylinder of Loam's engine is estimated at ten feet ; 

 an apparatus is fixed on it for registering the actual space passed over, 

 and the mean for five months was 9.913 feet. 



TABLE IIL — (Constants.) Dimensions of the Pump. 



* The stroke in this pump is but 5.5 feet. 



t This lift took its supply from the hot-well. 



J No correction has beeu applied for temperature, nor for isipurities con- 



