On the Blast Furnace in the Manufactitre of Iron. 173 
After the wood is completely charred, or the coal become coked, 
the subsequent changes are the same that happen in the charcoal 
furnaces. ‘ 
2.. Changes that take place in the ascending mass, which is com- 
posed of air and hygrometric motsture—The weight of the air 
thrown in at the tuyer in twenty four hours, is twice that of the 
ore, coal and flux, thrown in at the mouth during the same 
time. 
_ The air as soon as it enters the tuyer and reaches the first por- 
tion of coal, undergoes a change—its oxygen is converted into 
carbonic acid, and its moisture decomposed, furnishing hydrogen 
and carbonic oxide—after ascending a short distance, (12 or 18 
inches, ) the carbonic acid is converted into carbonic oxide—be- 
tween this point and the upper part of the boshes it under- 
goes but very little change, having added to it a further small 
amount of carbonic-oxide. So the ascending column at the top 
of the boshes is composed of nitrogen, carbonic oxide and hydro- 
gen—from this point it begins to undergo a change ; the carbonic 
oxide diminishes, carbonic acid appears, and goes on increasing 
for about half the way up the fire-room ; after which the carbonic 
acid, carbonic oxide and nitrogen remain the same, when the hy- 
drogen increases and moisture begins to appear and augment up 
to the mouth. The ascending mass as it passes out of the mouth, 
contains the vapor of water, carbonic acid, carbonic oxide, hydro- 
gen and nitrogen. The nitrogen undergoes no alteration in its 
passage through the furnace, and the same is true of the hydrogen 
_ formed at the tuyer. 
If wood be used, the gases passing out of the mouth are the 
same as those just mentioned, with an increased quantity of mois- 
ture, and the addition of those pyroligneous products arising from 
the dry distillation of wood. 
In case of the use of bituminous coal, the gases first alluded to, 
have added to them ammonia, light carburetted hydrogen, olefiant 
gas, carburetted hydrogen of unknown composition, and sul- 
phuretted hydrogen. 
3. The chemical reaction occurring between the ascending and 
descending masses.—F rom the foregoing statements, we can at a 
glance see what are the materials to be met with in the different 
parts of the furnace, and can therefore readily study their reac- 
tions upon each other. 
