nd flux, in their various
stages of transformation.

In order to explain clearly, and in as short space as possible, what
these transformations are, and how they are brought about, we may
consider:--1. The changes that take place in the descending mass,
composed of ore, fuel and flux. 2. The changes that take place in the
ascending mass, composed of air and its hygrometric moisture, thrown
in at the tuyer. 3. The chemical action going on between the ascending
and descending masses. 4. The composition of the gases in various
parts of the furnace during its operation. 5. The causes that render
necessary the great heat of the blast furnace.

1. _Changes that take place in the descending mass, composed of ore,
coal and flux._--By coal is here meant charcoal; when any other
species of fuel is alluded to, it will be specified. In the upper half
of the fire-room the materials are subjected to a comparatively low
temperature, and they lose only the moisture, volatile matter,
hydrogen, and carbonic acid, that they may contain; this change taking
place principally in the lower part of the upper half of the
fire-room.

In the lower half of the fire-room, the ore is the only material that
undergoes a change, it being converted wholly or in part into iron or
magnetic oxide of iron--the coal is not altered, no consumption of it
taking place from the mouth down to the commencement of the boshes.

From the commencement of the boshes down to the tuyer, the reduction
of the ore is completed. Very little of the coal is consumed between
the boshes and in the upper part of the hearth; the principal
consumption of it taking place in the immediate neighborhood of the
tuyer.

The fusion of the iron and slag occurs at a short distance above the
tuyer, and it is in the hearth of the furnace that the iron combines
with a portion of coal to form the fusible carburet or pig-iron. It is
also on the hearth that the flux combines with the siliceous and other
impurities of the ore. This concludes the changes which the ore, coal
and flux, undergo, from the mouth of the furnace to the tuyer.

If the fuel used be wood, or partly wood, it is during its passage
through the upper half of the fire-room that its volatile parts are
lost, and it becomes converted into charcoal. M. Ebelman ascertained
that wood, at the depth of ten feet, in a fire-room twenty-six feet
high, preserved its appearance after an exposure for 1 3-4 of an hour,
and that the mine