by the adoption of modifications made here and there in the arrangements
from time to time, as also by a determination not to be beaten, although
often disheartened, Mr. Foulis was ultimately rewarded with complete
success. The new system of firing being made so simple that there was
scarcely any possibility of failure likely to arise in ordinary practice
if it was superintended with but a moderate amount of care.

[Illustration: _Fig. 3._]

The results which were obtained in course of time with four ovens, or a
total of 32 retorts, were so exceedingly promising that it was forthwith
resolved to extend the new mode of firing to the whole of a double bench
of twelve ovens, now containing 96 retorts; and all the improvements
which had suggested themselves during the working experiments with the
four ovens were adopted from the first in the reconstruction of the
remaining eight ovens in the bench. More recently the regenerator system
has been applied to other 22 ovens, or 176 additional retorts, being the
whole of one of the main divisions of the retort house; and during the
very depth of the present winter, when the demand for gas was at its
greatest height, all the retorts of the converted or "Siemens" settings,
amounting to 272, were in full working activity, in which condition they
still remain. It is intended to make another very considerable extension
of the heat regenerative system of firing during the ensuing spring and
summer. The reconstruction of the present year will extend to the ovens
of seven retorts each, giving in this case eighty gas fired retorts; and
to twenty ovens of five retorts each, which will become sixteen ovens,
each having eight retorts, making 128 retorts in this division, and the
total being 208 retorts in place of 170 in the same amount of space. It
is confidently anticipated, therefore, that by the month of August of
the present year, 480 full sized retorts will be available for working