MANUFACTURE OF NATURAL CEMENTS. 231 



In the Rosendale district cylindrical kilns are used. These vary 

 from 8 to 12 feet in diameter and from 20 to 36 feet in height. A kiln 

 fed with one half ton of anthracite, pea size, will give 75 to 80 bar- 

 rels of cement per day. This is equivalent to a fuel consumption of 

 about 7 per cent on the weight of cement produced. From one fifth 

 to one third of the total produce of the kiln may be overburned clinker 

 or underburned rock. This item, however, depends largely upon the 

 skill of the burners, though it is also affected by uncontrollable factros, 

 such as temperature, weather conditions, force, and direction of the 

 wind, etc. 



The kilns in use in the Utica district in Illinois are elliptical in cross- 

 section (plan), with vertical walls. The largest kilns of this type are 

 30 feet in their longest inside diameter and 12 feet wide. Their total 

 height with foundation is 50 feet, giving a clear height of 45 feet from 

 bottom of draw-hole to top of kiln. These kilns turn out 400 barrels 

 (265 Ibs. each) of cement per day, taking 18 to 20 Ibs. of coal per barrel 

 of cement. This corresponds to a fuel consumption of only 6.8 to 7.5 

 per cent. 



The second size of Utica kilns is 20 feet by 9 feet in its inside diam- 

 eters. The smallest size is, like the others, elliptical, with inside diam- 

 eters of 14 and 7 feet, respectively, and a height of 32 feet from top 

 of bridge wall to top of kiln. These kilns turn out 300 to 375 barrels 

 per day. 



All the diameters quoted above are internal measurements. The 

 kiln-shell proper is of i-inch sheet iron. This is lined, successively, with 

 an 18-inch layer of ashes, 18 inches of stone or common brick, and 

 9 inches of fire-brick. 



The kilns in the central New York district are described * as egg- 

 shaped, 10 feet in diameter at the top, 12 feet at the middle, and 3 

 feet at the bottom, with a height of 28 to 42 feet. "There are usually 

 several kilns built together in an embankment of very heavy masonry, 

 so constructed against a hillside that the raw material can be conven- 

 iently conveyed there from the quarry and the burned cement easily 

 removed from the bottom of the kiln." The kilns are built of lime- 

 stone and lined either with sandstone or fire-brick. "When a kiln 

 is ready to be filled a cord of dry, hard, 4-foot wood is put into the bot- 

 tom and covered 4 inches deep with coarse anthracite coal, then a 

 layer 1 foot thick of cement rock, succeeded by another layer of coal 



* Luther, D. D. The Economic Geology of Onondaga County, New York. 

 15th Ann. Rept. N. Y. State Geologist, vol. 1, pp. 241-303. 1897. 



