in the Manufacture of Cast-Iron. 379 
sons, will appear on reference to a tabular statement supplied by 
Mr Dun or, 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. 3c 
