Calcarelle.—The earliest system adopted in Sicily was the calcarelle. This consisted simply of a stack of ore six to fifteen feet square, built in a ditch three or four inches deep, and whose floor was beaten hard and sloped to a single point, permitting the molten sulphur to flow out by an opening termed the morto. In building the stack, care was taken to put the largest pieces of ore at the bottom, selecting lumps of gradually diminishing size as the top was approached. The mass was ignited at the summit. The construction of the stack usually occupied two days; on the third day the sulphur escaped by the morto, and on the fourth the calcarelle was pulled down. The air necessary for the combustion of a portion of the sulphur (to afford the heat required to smelt the remainder) was freely admitted at all sides; only the mineral in the center of the heap was heated without actual contact with the air, so that its sulphur was melted out instead of being burned (oxidized). Consequently about 6,700 pounds of sulphur mineral were needed to afford 385 pounds of sulphur, or a yield of 5·7 per cent; as the ore contained thirty-five per cent of sulphur, the consumption of sulphur as fuel was 1,960 pounds, in order to extract 385 pounds. In addition, the immense volumes of sulphurous acid emitted from the stack caused a terrible destruction of the agricultural crops in the neighborhood.
Calcarone.—Nearly all the sulphur prepared in Sicily is now extracted by the calcarone (or calcherone, as it may also be spelled). This, as is shown in Figs. 1 and 2, is formed by building a circular
Fig. 1.
stone wall on an inclined sole. In front is the morto or outlet, having a height of four to six feet, and a width of two feet; over it is erected a wooden shelter for the workman in charge. Calcaroni may contain from two hundred to four hundred casse (each casse being equivalent to about six tons, and giving twelve to sixteen hundred-weight of sulphur). The durability of the calcarone is governed by
