128 
iron . 
worked by a water wheel. To these succeeded as a great 
Improvement in England, cast iron cylinders, in which a 
piston is worked by the power of a steam engine, (for in 
that country, iron works are very commonly put into ope- 
ration by the power of steam) of late (that is within these 15 
years) the mode generally pursued of equalizing the blast, 
is, by means of a column of water. Large iron chests are 
inverted in water, and the water between the outside con- 
taining- vessel, and the inside inverted- vessel, into which 
the air is thrown, serves to give by the re-action of its 
weight an equal pressure to the air thus thrown in, and 
which is again conveyed from the inverted chest into the 
tuyere. On this subject, I give the following essay from 
6 Phil Mag. 60, 113. 
“ When it is considered that in the smelting operation 
the reduction of immense quantities of materials is effect- 
ed by a compressed current of air impelled by the whole 
power of a blowing machine, the consequences of the 
change of air, either in quantity or quality, must be very^ 
obvious : when, farther, we contemplate the metal called 
into existence by means of combustion thus excited , 
when we consider iron as having the most powerful affini- 
nitv for the base of that part of the air which maintains 
combustion ; and when we view the debased state to 
which the metal is reduced by coming into improper contact 
with it, we must conclude, that the application of blast 
m the manufacturing of iron, calls for the most minute 
and thorough investigation. In order to take a compre- 
hensive view of this subject, the following division will 
be requisite 
1st, The Intimate connection which the quantity of 
blast bears to the area of the internal cavity of the furnace, 
and to the nature of the pit-coal* 
2d, The various modes by which air is procured, and 
how these respectively affect the quality of the air. 
