may be necessary to have a shallow ingot pit (20 to 24 inches deep); but
with cupolas this will not generally be necessary, and the whole of the
operations may be carried on at the ground level. Each crane is intended
to be supplied with two or three converters, so that operations may be
carried on continuously. The weight of charge proposed is 15 cwt., which
should under ordinary conditions give 12 cwt. of ingots. Taking the time
of a single converting operation at half an hour it will be easy to
obtain fifty blows per day, or a production of 30 tons. This may be
easily increased by placing a second converting crane on the other side
of the furnace, for which the same blowing engine will be sufficient, as
the actual blowing time will not exceed twelve minutes. The labor
required for each converter will be about six men per shift.

The blast required has been experimentally determined at 40-50 cubic
meters per minute at 15 lb. pressure. This will be supplied by a single
cylinder engine of 900 millimeters blast, and 786 millimeters steam
piston, diameter 786 millimeters, stroke making fifty revolutions per
minute, which is also to work a Root blower and the accumulator pumps.
Having regard to these very different demands upon the power of the
engine, it will be provided with expansion gear, allowing a considerable
variation in the cut-off. A single boiler of 70 to 75 square meters
heating surface will be sufficient. The accumulator is intended to work
at 300 lb. pressure.

The cost of the plant, including one of each of the following items,
converter, converter truck, blowing engine, accumulator, ingot crane,
centesimal weighing machine, and accumulator pump, is estimated at £2,050
to £2,100; and that of the steam boiler, £325. The buildings may be of
the simplest and cheapest possible character. As the productive power of
such a plant contrasts very favorably with its cost, the author considers