in the Manufacture of Cast-iron. 379 



sons, will appear on reference to a tabular statement supplied by 

 Mr Dunlop, and printed as an Appendix to this paper. Not 

 further to dwell on such details, I proceed to the last division of 

 this paper, which is, 



IV. To attempt an explanation of the foregoing extraor- 

 dinary results. 



Subsidiary to this attempt, it is necessary to discriminate be- 

 tween the quantity of fuel consumed and the temperature pro- 

 duced. For instance, we may conceive a stove to be kept at the 

 temperature of 500° Fahrenheit, and lead to be put into such 

 a stove for the purpose of being melted. Then, since the melt- 

 ing point of lead is more than 100° higher, it is evident that 

 whatever fuel might be consumed in keeping that stove at the 

 temperature of 500°, the fuel is all consumed to no purpose, so 

 far as regards the melting of lead, in consequence of deficiency 

 in the temperature. In the manufacture of cast-iron likewise, 

 experience has taught us, that a certain temperature is required 

 in order to work the furnace favourably, and all the fuel con- 

 sumed so as to produce any lower degree of temperature, is fuel 

 consumed in vain. And how the hot blast serves to increase 

 the temperature of a blast furnace, will appear on adverting to 

 the relative weights of the solid and of the gaseous materials 

 made use of in the reduction of iron. 



As nearly as may be, a furnace, as wrought at Clyde Iron- 

 works in 1833, had two tons of solid materials an hour put in at 

 the top, and this supply of two tons an hour was continued for 

 23 hours a-day, one half-hour every morning, and another every 

 evening, being consumed in letting off the iron made. But the 

 gaseous material — the hot air — what might be the weight of it ? 

 It can easily be ascertained thus : I find, by comparing the 

 quantities of air consumed at Clyde Iron-works, and at Calder 

 Iron-works, that one furnace requires of hot air from 2500 to 

 3000 cubical feet in a minute. I shall here assume 2867 cubi- 



VOL. XIII. PART II. 3 c 



