126 
Iron a 
most every trial in England, the produce of the fur- 
nace has been encreased by encreasing the quantity of 
air in modem furnaces, beyond the common blast of the 
furnaces formerly erected. I believe the newly built fur- 
naces of England, have two bellows-arches opposite to 
each other, and two air pipes. This not only encreases the 
quantity of air admitted, but in a considerable degree pre- 
serves the nose of the tuyere from burning, and the pipe 
need not project so far into the furnace ; nor is it found 
that the opposite currents of air obstruct each other. This 
encrease of the volume of air in modem works, may , for 
aught I know, be more advantageous in the pit-coal fur- 
naces, than in the wood-charcoal furnaces; but I am 
strongly inclined to think that there is great room for im- 
provement in this respect, even among our charcoal fur- 
naces of Pennsylvania. The following remarks of Mr. 
Roebuck, one of the owners and managers of the Devon 
iron works, are considered as having been confirmed by all 
late experience. 6 Ph. Mag. 33 L 
£i This improper measure, however, afforded me the op- 
portunity of immediately putting in practice the plan 1 
have mentioned. 
When one of the furnaces was stopped, the other 
continued to be blown by a blow-pipe of two and three 
fourth inches diameter, and the produce of the furnace, 
for several weeks thereafter, was not 20 tons of iron per 
week at an average. The engine at this time was making 
about 16 strokes a minute, with a stroke of the air-pump, 
about 4 feet 8 inches long ; but when I altered the di- 
ameter of the blow-pipe, first to 3, and immediately after 
to three and one-fourth inches diameter, and regulated the 
working gears of the engine, so as to make a stroke of 
five feet two inches long, and about 19 strokes in a mi- 
nute, on an average, the produce was immediately increas- 
ed, It continued to be, on an average of nine months 
/ 
