324 TUBULAR BOILER, SUPERHEATING STEAM, 



by 471, being ike inches of steam made by 1 inch of water 

 divided by 243, the degrees of heat raised by the coal, gives a 

 product of 116 ; therefore, by Mr. Watt's view it appears that 

 low steam would do one-fifth more duty than high steam, and yet 

 Binner Downs engine in actual work performs about four times 

 the duty given by Mr. Watt's theory and practice, with only 

 one-sixth part of the amount of heat carried off by the con- 

 densing water, proving that high steam has much less heat, in 

 proportion to its effective force ; and this is further proved by 

 the small quantity of condensing water required to extract its 

 heat. 



" Yesterday I proved this 70-inch cylinder while working 

 with the fire-flues round it, which flues only consumed 5 bushels 

 of coal in twenty-four hours. The engine worked eight strokes 

 a minute, 10-feet stroke, 11 Ibs. to the inch effective force on the 

 piston ; steam in the boiler 45 Ibs. above the atmosphere, con- 

 suming 12 bushels of coal in four hours, using 13 gallons of 

 condensing water at each stroke, which was heated from 70 to 

 104 ; but when the fires round the cylinder were not kept up, 

 though still having the casing of hot brickwork around it, and 

 performing the same work, burnt 17 bushels of coal in the same 

 time of four hours, and required 15 J gallons of condensing 

 water, which was heated from 70 to 112. You will find that 

 the increased consumption of coal, by removing the fire from 

 around the cylinder, w r as nearly in the same proportion as the 

 increase and temperature of the condensing water, showing 

 the experiment to be nearly correct. 



" From the general reports of the working of the engines it 

 appears that when the surface sides of the castings are heated, 

 either by hot air or high steam, the duty increases nearly 

 fifty per cent, from this circumstance alone. 



"A further proof of the more easy condensation of high 

 steam was in the Binner Downs 42-inch cylinder engine, 9-feet 

 stroke, six strokes per minute, 11 Ibs. effective power on each 

 inch, burning 1| bushel of coal an hour. In this engine the 

 proportion of saving by the heating flues was the same as in 

 the large engine. I tried to condense the steam by the cold 

 sides of the condenser, without using inject ion- water. The 



