IRON MANUFACTURE. 531 
in the form and dimensions of the pipes, the arrangement of the stoves 
themselves being practically the same in all cases. The gas being ad- 
mitted with a sufficient quantity of air into a series of two or more 
arched chambers, 4 to 5 ft. high by 33 to 4 ft. wide; these combustion 
chambers connect through a series of flues or openings with a space 
above, in which the pipes which convey the blast are located, and the 
flame resulting from the combustion of the mixed gas and air circulates 
round the pipes which fill the chamber. The whole is built of fire- 
brick, and braced by iron tie-rods to prevent cracking and injury by 
heat. The blast does not go through one continuous pipe, but is sub- 
divided, and passes through a number of pipes arranged in parallel 
order, the object being to diminish the amount of friction and conse- 
quently loss of pressure in passing through the stove. 
In order to effect complete and proper combustion of the gas, air 
must be admitted with it, which is done by means of a jet, through which 
air is brought to the center of the gas flue, as in the compound blow- 
pipe. The simplest arrangement of pipes is that of a siphon or pipe 
bent on itself in the pattern seen in the old ‘‘ Calder” oven, figured in 
books on Metallurgy. The large amount of room taken up by such 
pipes, together with the fragile character of the casting, has led to their 
universal abandonment, and many patterns are at present in use in this 
State, each supposed to present peculiar advantages, either as to dura- 
bility of pipe, simplicity of construction, or ease in replacement. One 
of the best-known in the Mahoning Valley of these ovens is the 
“Hamilton” hot-blast stove, manufactured at Youngstown, and in use 
at several points there. Its peculiarity consists in having the pipes 
double and concentric, by which the air passes up through one pipe to 
the extremity of the enveloping pipe; this construction is shown in 
Figure VII. 
The division of the air is well shown in this sketch, the blast 
passing into the stove through a long pipe or box, and dividing itself 
through the nine pipes connected therewith. The blast passes from one 
of these boxes or ‘“‘bed-pipes” to the next, and so may be brought to 
a temperature only limited by the material and durability of the pipes. 
Another usual form of hot-blast stove has the pipes made in U-shape 
more or less united throughout their length by cross-bars; these are 
arranged in rows on two parallel “bed-pipes” in the stoves. Another 
form of stove has the blast-pipe section, a flattened oval divided through- 
