159. _Q._--Is the use of the dead plate universally adopted in Boulton and
Watt's land boilers?

_A._--It is generally adopted, but in some cases Boulton and Watt have
substituted the plan of a revolving grate for consuming the smoke, and the
dead plate then becomes both superfluous and inapplicable. In this
contrivance the fire is replenished with coals by a self-acting mechanism.

160. _Q._--Will you explain the arrangement of the revolving grate?

_A._--The fire grate is made like a round table capable of turning
horizontally upon a centre; a shower of coal is precipitated upon the grate
through a slit in the boiler near the furnace mouth, and the smoke evolved
from the coal dropped at the front part of the fire is consumed by passing
over the incandescent fuel at the back part, from which all the smoke must
have been expelled in the revolution of the grate before it can have
reached that position.

161. _Q._--Is a furnace with a revolving grate applicable to a steam
vessel?

_A._--I see nothing to prevent its application. But the arrangement of the
boiler would perhaps require to be changed, and it might be preferable to
combine its use with the employment of vertical tubes, for the transmission
of the smoke. The introduction of any effectual automatic contrivance for
feeding the fire in steam vessels, would bring about an important economy,
at the same time that it would give the assurance of the work being better
done. It is very difficult to fire furnaces by hand effectually at sea,
especially in rough weather and in tropical climates; whereas machinery