Improved Kilns for burning Lime. 
133 
win afterwards explain) 1^ inch diameter, with a space of about 
1 inch between them. They should be formed with blunt points 
at one end, and tlie middle bars should have an eye at the other 
end, so as to enable a crowbar to be passed through them. It is 
better to make the middle bars about 1 foot 6 inches longer 
than the opening they have to cover, in order to obtain a firmer 
hold of them when they require to be withdrawn. 
An opening should be left in the front wall of the kiln imme- 
diately above the fire-bars, which should be supported by a strong 
wrought-iron frame, 3 inches wide, securely built into the brick- 
work. This opening is for the purpose of gaining access to the 
interior of the kiln, in order to light the fire or to assist in re- 
moving the lime when it wedges itself together in a mass, and 
svill not pass down through the fire-bars in the usual way. 
Fig. 1. — Section of Common Perpetual Kiln icith central furnace. 
To start the kiln, a fire is lighted on the fire-bars, and as soon 
■as it burns briskly enough, the hole already described is securely 
bricked up, and the fire fed with lumps of coal from the circular 
■platform round the top of the kiln. When the fire is sufficiently 
'ignited, lumps of chalk or limestone are, in like manner, thrown 
upon the fire, to a thickness of about 12 inches ; and as soon as 
the fire appears to burn well through this layer, a layer of coal, 
and, shortly afterwards, another layer of chalk or limestone, are 
added ; and, if the fire continues to burn well, the whole kiln may 
^■be filled with alternate layers of chalk or limestone and coal. 
The proportion of coal to be used must be determined by trial, 
