lone would prevent
its being used as a cheap source of hydrogen; the next point was that
when steam was passed over the red-hot iron, the temperature was so
rapidly lowered that the generation of gas could only go on for a very
short period, while, finally, the swelling of the mass in the retort
and fusion of some of the magnetic oxide into the side renders the
removal of the spent material almost an impossibility. These
difficulties can, however, be got over. Take a fire clay retort, six
feet long and a foot in diameter, and cap it with a casting bearing
two outlet tubes closed by screw valves, while a similar tube leads
from the bottom of the retort. Inclose this retort by a furnace
chamber of iron lined with fire brick, leaving a space of two feet six
inches round the retort, and connect the top of the furnace chamber
with one opening at the top of the upright retort, while air blasts
lead into the bottom of the furnace chamber, below rocking fire bars,
which start at bottom of the retort, and slope upward, to leave room
for ash holes closed by gas tight covers. The retort is filled with
iron or steel borings, alone if pure hydrogen is required, or cast
into balls with pitch if a little carbon monoxide is not a drawback,
as in foundry work. The furnace chamber is now filled with coke, fed
in through manholes, or hoppers, in the top, and the fuel being
ignited, the blast is turned on, and the mixture of nitrogen and
carbon monoxide passes over the iron, heating it to a red heat, while
the fuel in contact with the retort does the same thing.

When the fuel and retort full of iron are at a cherry-red heat, the
air blast is cut off, and the pipe connecting the furnace and retort,
together with the pipe in connection with the bottom of the retort,
are closed, and steam, superheated by passing through a pipe led round
the retort or interior wall of the furnace, is injected at the bottom
of the red-hot mass of iron, which decomposes it, forming magnetic
oxide of iron and hydrogen, which escapes by the second tube at the
top of the retort, and is led away either to a carbureting chamber if
required for illumination, or direct to the gasholder if wanted as a
fuel. The mass of incandescent fuel in the furnace chamber,
surrounding the retort, keeping up the temperature of retort and iron
sufficiently long to enable the decomposition to be completed.

The hydrogen and steam valves are now closed and the air blast turned
on. Th