140 
Improved Kilns for burning Lime. 
lime. Iron doors are made in the ash-pits, through which 
the ashes are alkiwed to fall on to the floor on which the lime is 
withdrawn. Ventilating pipes should be carried from this floor, 
through the firing-chamber, to relieve the workmen from the 
great heat while the lime is being withdrawn. The fuel used in 
these kilns is wood, 1 lb. being required to burn 3 lbs. of lime; 
but coal is also used in the variety of kiln possessing a com- 
bustion-chamber. The kiln is charged by filling it with lime 
up to the height of the draught-holes, in which the fire is lighted 
and kept burning, and, when this charge is thoroughly burnt 
through, the kiln is completely filled, the limestone being first 
packed in courses and then thrown in from the top. The fire is 
then drawn back from the draught-holes on to the fire-grates, 
and the work of the kiln proceeds, the limestone being thrown 
in from the top, and withdrawn from the bottom when burnt. 
These kilns are usually drawn every 12 hours, a similar lapse 
of time being required to enable the lime to cool down suffi- 
ciently to allow it to be removed. They are sometimes con- 
structed with one fire-grate and a combustion-chamber, where 
a considerable amount of air is supplied by draught-holes 
behind the bridge, and the fire is brought to a very great in- 
tensity before it enters the shaft of the kiln. In some kilns 
the withdrawing floor for the lime is constructed at such a level 
that a railway truck can pass underneath it to be loaded with 
lime. 
In all cases it is necessary to construct a bridge, with a tram- 
way laid upon it from the chalk or limestone hill to the top of 
the shaft, to supply the materials to the kilns ; and a good road 
should be formed, at the level of the withdrawing floor, to convey 
away the lime and ashes, and to bring in the fuel, which can be 
raised by a simple lift to the floor above, 
IV. — Improved Perpetual Kiln. 
I will now describe a kiln of my own invention, not specially 
designed for the purpose of burning lime, but for the purpose 
of drying clay previously to grinding for fire-brick making. A 
few slight modifications, however, will adapt it to the purpose of 
lime-burning, and I will describe it with such alterations. 
It will be seen that it answers to the sort of kiln I referred to 
in commencing the description of the perpetual kilns heated by 
fires from beneath ; and that it can either be used as a perpetual 
kiln, from which a large and continuous supply of lime can be 
drawn, or as a perpetual kiln with a moderate supply, or, in 
like manner, as an intermittent kiln, from which either a large 
or moderate charge can be drawn. 
The form and dimensions are particularly shewn in Figs. 7 
