Iron. 
193 
I shall now proceed from mere calculation to matter of 
fact, and attempt to prove the correctness of the former 
by the approximation of the latter to its results. Let a 
blast-furnace be supposed to produce 20i tons of pig- 
iron per week, = 45360 avoirdupois pounds; this, di- 
| ;i vided by days, hours, minutes, and seconds, gives per 
day 6480 pounds, per hour 270, per minute 4f lb., and 
per second 525 grains. 
From this it is evident that 1 lb. of cast iron is produced 
in 13 toV seconds : experience has shewn that a blast-fur- 
nace, producing, in any of the above periods, the respec- 
tive quantity of metal, requires a discharge of air per mi- 
nute nearly equal to 1350 cubic feet ; this, divided by 
4,51b. the quantity produced per minute gives, for 11b. 
iron, 300 cubic feet. The quantity, by calculation, we 
have seen to be 281 cubic feet — difference 19 : a sum no 
way considerable when we reflect upon the inequality of 
the movements of a blowing machine, and when it is re- 
collected that some allowance ought also to be made for 
what air may pass through the furnace undecomposed, or 
may be lost at the place of entrance. 
From this coincidence of theory with practice, we can- 
i not help admiring the rigorous principles on which the 
Lavoiserian system is founded ; nor are we less pleased 
to find, that, small as the operations of the chemist may be, 
yet they are a just epitome of what takes place in the phi- 
losophy of extensive manufactories. The following table 
exhibits the quantity of carbon which may be used upon 
an average, with the relative quantity of carbonic acid 
formed, and air used : 
In the manufacture of 
1 lb. - 
- 1 ton of iron, 
The pure carbon requisite is 
2-49 - 
- 5585-44 lb. 
Carbonic acid formed 
81-86 - 
183366*40 cub. feet 
Oxygen gas used 
75-89 - 
— 169993.60 cub. feet 
Atmospheric air employed 
281-00 - 
- 629440*00 cub. feet 
B B 
