100 CEMENTS, LIMES, AND PLASTERS. 



for charging the kiln with stone and the bottom for supplying fuel 

 and drawing out the lime. In charging, the largest pieces of limestone 

 were first selected and formed into a rough dome-like arch with large 

 open joints springing from the bottom of the kiln to a height of five 

 or six feet. Above this arch the kiln was filled from the top with frag- 

 ments of limestone, the larger pieces being used in the lower layers, 

 these being topped off with fragments of smaller size. A wood fire 

 was then started under the dome, the heat being raised gradually to 

 the required degree in order to prevent the sudden expansion and con- 

 sequent rupture of the stones forming the dome. Should this happen, 

 a downfall of the entire overlying mass would take place, putting out 

 the fire and causing the total loss of the contents of the kiln. After a 

 bright heat was once reached throughout the mass of stone, it was 

 maintained for three or four days to the end of the burning. This was 

 indicated by a large shrinkage in volume of the contents of the kiln, 

 the choking up of the spaces between the fragments, and the ease with 

 which an iron rod could be forced down from the top. The fire was then 

 allowed to die out and the lime was gradually removed from the bottom. 

 It was in this manner that all the lime used in Indiana for many years 

 was burned, and in some localities these temporary intermittent kilns 

 are still in operation. The process of burning is simple and cheap, 

 the only expense being for blasting the stone and preparing the fuel. 

 Possibly but one or two kilns were necessary to supply a neighbor- 

 hood for a year. These were operated for a week or two when required 

 and remained idle for the remainder of the year. 



"As the population increased, the demand for lime became greater, 

 and in many places permanent kilns lined with fire-brick were erected. 

 These were the old-fashioned stone ' pot-kilns ' of a quarter century ago. 

 On the inside they were usually circular in horizontal section, tapering 

 slightly, by a curve both up and down, from the circle of largest diameter, 

 which was from 4 to 6 feet above the bottom. A kiln 10 to 11 feet 

 in greatest diameter was 25 to 28 feet high, 5 to 6 feet in diameter at 

 the top and 7 to 8 feet at the bottom. There was an arched opening 

 on one side at the bottom 5 or 6 feet high, through which the wood 

 was introduced and the burnt lime removed. A horizontal grating 

 on which the fire was built was usually placed 1 or 2 feet above the 

 bottom. 



"In all these intermittent kilns there was an enormous loss of heat 

 at each burning, for the quantity of fuel necessary to raise the contents 

 of the kiln and the thick stone and brick walls to the necessary degree 

 of heat had to be repeated each time the kiln was charged. Moreover, 





