linker and fine ash varies from
22 to 37% of the bulk dealt with. From 25 to 30% is a very usual
amount. At Shoreditch, where the refuse consists of about 8% of straw,
paper, shavings, &c., the residue contains about 29% clinker, 2.7%
fine ash, .5% flue dust, and .6% old tins, making a total residue of
32.8%. As the residuum amounts to from one-fourth to one-third of the
total bulk of the refuse dealt with, it is a question of the utmost
importance that some profitable, or at least inexpensive, means should
be devised for its regular disposal. Among other purposes, it has been
used for bottoming for macadamized roads, for the manufacture of
concrete, for making paving slabs, for forming suburban footpaths or
cinder footwalks, and for the manufacture of mortar. The last is a
very general, and in many places profitable, mode of disposal. An
entirely new outlet has also arisen for the disposal of good
well-vitrified destructor clinker in connexion with the construction
of bacteria beds for sewage disposal, and in many districts its value
has, by this means, become greatly enhanced.

[Sidenote: Forced draught.]

Through defects in the design and management of many of the early
destructors complaints of nuisance frequently arose, and these have,
to some extent, brought destructor installations into disrepute.
Although some of the older furnaces were decided offenders in this
respect, that is by no means the case with the modern improved type of
high-temperature furnace; and often, were it not for the great
prominence in the landscape of a tall chimney-shaft, the existence of
a refuse destructor in a neighbourhood would not be generally known to
the inhabitants. A modern furnace, properly designed and worked, will
give rise to no nuisance, and may be safely erected in the midst of a
populous neighbourhood. To ensure the perfect cremation of the refuse
and of the gases given off, forced draught is essential. This is
supplied either as air draught delivered from a rapidly revolving fan,
or as steam blast, as in the Horsfall steam jet or the Meldrum blower.
With a forced blast less air is required to obtain complete combustion
than by chimney draught. The forced draught grate requires little more
than the quantity theoretically necessary, while with chimney draught
more than double the theoretical amount of air must be supplied. With
forced draught, too, a