LIME-BURNING. 109 



cipitated is mixed 'with clay and burned into Portland cement. An 

 editorial note appended to Mr. Mather's article states that the Har- 

 greaves-Bird alkali-works at Middlewich, England, also use waste car- 

 bon-dioxide gas from lime-kilns. 



Cost of lime-manufacture. With the exception of a comparatively 

 few large and well-managed lime-plants, lime-manufacture in the United 

 States is not so steadily and economically handled as to give much 

 basis for generalizations concerning costs. The result is that the data 

 obtainable are rarely definite enough to be of much service. The follow- 

 ing is probably as fair a statement of the case as can be made. 



The principal items to be considered in estimating the cost of lime- 

 manufacture are: 



(1) Interest on cost of plant and quarry. 



(2) Cost of quarrying limestone. 



(3) Cost of fuel for burning. 



(4) Labor costs, exclusive of quarry. 



The interest on cost of plant and quarry will vary greatly according 

 to the steadiness with which the plant is operated. This is, of course, 

 true with regard to the same item in the cement industry, but lime- 

 plants are in general subject to greater fluctuations in output. The 

 estimates given below of interest charges per ton of lime are therefore 

 given a very wide limit, but it is believed to be impracticable to place 

 them more definitely. 



The cost of quarrying is also variable, but within narrower limits* 

 In large, carefully managed quarries located near the kilns, and with 

 stone and stripping so arranged as to admit of cheap extraction, the 

 cost of quarrying the limestone and transporting it to the kiln may fall 

 as low as 25 cents per ton. This cost is attained in Portland-cement 

 quarries in the Lehigh district of Pennsylvania, and in a number of 

 natural-cement and lime quarries elsewhere. On pages 378, 379 will 

 be found further details as to cost of quarrying, one of the examples 

 being of the costs at a quarry worked both for Portland cement and 

 for lime. With average skill in locating and managing the quarry, 

 it is probable that the cost of quarrying need never rise above 40 or 

 45 cents per ton of rock. Allowing for waste and loss by under or over- 

 burning, 2 tons of limestone will be required to make 1 ton of lime, 

 'his would give as the probable limits of cost of quarrying 50 to 90 

 cents per ton of burned lime. 



Wood is still used for fuel at many lime-kilns, in which case the cost 

 )f fuel may be merely nominal or may be very high. When coal is 

 sed for fuel in a modern kiln, the coal consumption per ton of burned 



