Mr. Hen wood on the Cornish Pianping-Engmes. 487 



Table II. — (Variables.) 



Qiiantities of water and steam^ pressures of steam, and tempera- 

 tures. 



Mines and Engines. 



Iluel Towan, Wilson' 

 Dinner Downs, Swan' 

 , Burn' 



EastCriunis, Hudson' 

 Iluel Vor, Trelawny' 

 , Borlase's 



Water in Boil, 

 ers*. Cubic feet. 



1096 

 686 



2000 



984 

 586 



1820 



1080 

 636 

 884 

 1920 

 1164 

 2290 



Steam in Boilers*, 

 Cubic feet. 



730 



550 



Pressure of Steam 

 in the Boilers, lbs. 

 per square inch . 



77-25 

 74-78 



36-82 



47-25 

 58-07 



26-32 



64-1 



67-87 



55 



31-68 



47 



40 



Temperature of 

 Hot-wellf. 



93-8 

 89-24 



82 



Mines and Engines. 



Temperature of 



Condensing 



Water. 



Iluel Towan, Wilson's 

 Dinner Downs, Swan's 

 , Burn's 



East Crinnis, Hudson's 

 Huel Vor, Trelawny's 

 , Borlase's 



66-5 

 56 



G7-5 



66 



64-72 

 52-32 



Temperature of 

 Boiler-shed. 



78-5 

 108 



68 



74-75 

 73-75 



64-5 



66-2 



Temperature of Temperature of ex. 

 Engine-room. ternal Air. 



77-5 

 73 



55 



75-28 

 66-48 



61-8 



56-5 

 56-5 



50 



52-5 

 49 



40-75 



53-84 

 52-56 



45 



Note to Table IF. 

 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 ex- 

 tensive mining establishment,) as the only machine the evaporation in which 

 has been published. See Mr. Lean's Report in the Cornwall Polt/technic 

 Society's Transactions, IV. (1836) p. 34. 



Loam's engine, at the United Mines, has the steam cylinder of 85 inches 

 in diameter, the stroke in it is 10 feet, and in the pump 7-5 feet; the load 

 is about 12 lbs. per stjuarc inch of the area of the piston, and the velocity 

 about 4"8 strokes per minute : the elasticity of the steam employed I am 



* The boilers were, of course, always full of water and steam ; and as the 

 quantity of one increased, that of the other diminished, and rice versa. 



t As the pressure of the steam in the boilers increased, tlic tem|)craturc 

 of the hot-well declined; so that by observing the alteration in one, that 

 of the other could be jircdicted with great certainty. 



