240 
THE SMOKE ABATEMENT EXHIBITION. 
The Martin fire door is balanced by a weight, so that it 
remains in any position in which it is placed. 
Ferret’s Multiple Stage Furnace is composed of four fire clay 
stages or shelves, slightly domed, and of an ashpan. The front 
is furnished with three doors, over each other. Two of these 
doors serve for manipulating the fires on the stages, and the third 
in the ashpan for extracting the ashes. The combustion is effected 
with hot air. The front plate is double, and in this the air is 
heated before it passes into the furnace. It is admitted at the 
bottom, and takes an upward direction. By this furnace, fuel with 
a very small percentage of combustible matter, can be burned. 
The inventor claims that any fuel, with only 25 per cent, of com- 
bustible matter, may be consumed in this apparatus. Certainly 
the refuse, ashes, and small coal which was disposed of in the Ex- 
hibition seem to prove that for purposes in which rapid combustion 
is not required, such as, for instance, in supplying hot water for 
heating purposes, this furnace would prove extremely economical. 
In Barber’s Smokeless Furnace the grate is sloping, the fresh 
fuel being fed in under the other at three different levels. After the 
fire is started the fresh fuel must be kept in front of the burning 
coals, so that the air passes first over the fresh fuel. The coal is 
thrown on the shelves frequently and in small quantities. It is 
then pushed forward, so that it carries the previously-coked fuel 
before it. The fuel is fed in at the bottom first, and then on the 
shelf above, and so on, and care must be taken that the fresh 
fuel shall not project above the coked fuel above it. If it does, 
some of the coked fuel is to be spread over it so as to cover it 
from the shelf above. All the sloping bars must be kept covered 
with fuel so that cold air may not rush in and cool the fire. 
Besides those that I have, described, there are many other 
forms of mechanical feeding apparatus which time prevents me 
from alluding to here. This department of the Exhibition has 
received much attention. 
