134 
ImproiKct Kilns for burning Lime. 
as it differs greatly according to the nature of the material, the size 
of the lumps, and the sort of coal used. On the average, chalk 
will burn if the proportions are 1 of coal to 7 of chalk ; but, for 
limestone, they vary from 1 to 1^ of coal to 6 of limestone. 
When once the kiln is set properly going, it ought not to 
require any rekindling, but to continue in operation for months 
together, by supplying fresh materials at the top of the kiln as the 
lime is drawn away at the bottom. The kiln is usually drawn 
once every twenty-four hours, by drawing out the middle fire-bars ; 
and as it is sometimes a difficult matter to start them, owing to 
the pressure, it is better to make them circular in section, so that, 
by introducing a crowbar through the eyes at the ends, they can 
readily be turned round, and partly freed from the pressure. 
If the lime does not fall out easily it can be loosened by a bar, 
with the end turned up, which is introduced between the fire- 
bars and drawn backwards and forwards ; or a few of the bricks 
can be withdrawn from the opening above mentioned for lighting 
the fire, and the lime forced down with a heavy bar. The lime 
is then drawn to the front of the archway with an iron hoe, and 
left till it is cool enough to be measured and run into the store- 
shed or carted away. 
The drawing being completed, the fire-bars are driven back 
again into their places and left for another twenty-four hours, 
during which time the filling is continued on the top, as above 
mentioned. For this purpose it is desirable for the kiln to be 
so placed that a tramway may be laid over the top or along one 
side of it — preferably the latter, as it gives more opportunity for 
properly spreading the alternate layers of coal and calcareous 
material. It is better also to have a broad platform round the 
top of the kiln, to give room for depositing a quantity of coal, 
as it can seldom be unloaded direct from the truck. 
Some kilns have been constructed with an inverted truncated 
cone placed, byway of a shaft, upon the under cone (Fig. 2), in order 
to retain the heat, and an arched opening in the outer wall for the 
purpose of feeding the kiln. From experience obtained in carrying 
out the same principle with brick-kilns, I am of opinion that very 
little advantage is gained by such an arrangement, unless an inner 
flat crown, pierced with holes, is also constructed upon the under 
cone before the upper cone is carried up (Fig. 3). It would, 
however, be extremely expensive, and, in fact, almost impos- 
sible, to carry out the proper system of loading a kiln of this 
description with such an arrangement. 
Kilns have also been constructed of an elliptical instead of a 
conical section, or, to speak more correctly, of an egg section 
with the two ends cut off. This section has no doubt some 
advantages, as it conducts the heat better to the top of the kiln, 
and also, to some extent, assists the descent of the lime ; but it 
