Improved Kilns for burning Lime. 
139' 
1. That the whole of the lime, with a very small exception, is 
thoroufjhly calcined. 
2. That no stones, cinders, or other impurities, are found mixed 
up with the lime. 
3. That if .the kiln described, with the central fire, is used, 
the savin» of fuel will be fully one-fourth over the best " Per- 
petual Kiln." 
The disadvantages are : — 
1. That the upper 1 foot G inches of the lime can never be 
properly calcined. 
2. That the labour of setting, burning, and drawing these 
kilns is considerably greater, and, therefore, more expensive 
than that required for the perpetual kilns. 
3. That when a large and constant supply of lime is required, 
the quantity produced is very much less than by the perpetual 
kilns. 
4. That the cost of building these kilns properly is con- 
siderably greater than that of the perpetual kilns. 
III. The Intermitti nt or Perpetual Kiln. 
The third description of kiln used for lime- burning is one 
much less generally known than the two already described. 
Properly speaking it is a perpetual kiln, but it is heated by 
furnaces from beneath. It can be most advantageously used as 
a perpetual kiln, by supplying the material to be calcined at 
the top, and withdrawing it at the bottom ; but, in a form I will 
describe, it may also be used as an " Intermittent Kiln " by 
filling the kiln, and withdrawing the charge, when the burning 
is completed, altogether through the hatchway. 
These kilns cannot be built in the side of a hill, but they must 
be so constructed as to be accessible on all sides. They usually 
have a circular or hexagonal shaft in the centre, from 40 to 
60 feet in height, varying from 7 feet to 10 feet in diameter, 
and tapering from the top to the middle, and again from the 
middle to the fire-grate. From 3 to 5 furnaces are constructed, 
round the outside of the shaft, the fire-grates, which are generally 
constructed of perforated fire-tiles, being made sufficiently large 
to span from wall to wall, or being supported on iron bearers. 
The fire passes out of the furnace through a hole in the end wall 
into the centre shaft. 
The withdrawing holes, or hatchways, are situated between^ 
and below the ash-pits of the fire-holes ; and are closed by cast- 
iron doors to prevent unnecessary cooling of the kiln. The floor 
to the fire-chamber forms the roof to the withdrawing floors^ 
The hatchways are widened from the centre towards the outside, 
and are also inclined outwards to facilitate the withdrawal of the 
