in the flues under the oven bottom. This is really all the plant
required. It should be remarked that these bottom flues are carried to
different points of the side walls, and the products of combustion are
allowed to rise upward into the oven through gaps left for the purpose.
A supplementary supply of heated air is provided to help the combustion
of the gas in these flues, which would otherwise be languid. When the
gas is turned on from the main cock in the furnace either to the top or
the bottom set of burners, a long match is used to light them from
the same point. This is effected without risk of firing back, by the
adoption of a specially constructed atmospheric nipple and shield, the
pattern of which is registered. The flame from the top burners unites in
a sheet of fire, which spreads out all over the crown of the oven, at
the same time that the burners below are doing their work, and the
products of combustion flow together through the oven to the chimney,
which is the same that was used for coal. At first, as might be
expected, there was considerable difficulty in finding the most suitable
position of the chimney damper, aggravated in this case by the fact that
the other oven worked with a coal fire into the same shaft. Finally,
however, the two flues were disconnected with the happiest results.
During the past fortnight the oven has been in regular use, and the
bread has been sold over the counter in the ordinary course of trade.
Two and three batches of bread have been baked in one day in this oven;
the economy of its use, of course, increasing with the number of loaves
turned out. As a rule the gas is lighted for about an hour before the
oven is wanted, and about 250 cubic feet are used. Then the cocks are
shut and the oven is allowed to stand closed up for ten minutes, in
which time it ventilates itself, and the heat spreads over it. Then the
batch is set, and the baking occupies from an hour to an hour and a
half, according to the different classes of loaves. Two batches are
baked with a consumption of about 620 cubic feet of gas; costing, at 2s.