488 



THE POPULAR SCIENCE MONTHLY. 



the care exercised in its construction ; ten years is not an unusual 

 period. The charging of the calcarone is a matter of primary impor- 

 tance, as on it depends the yield of sulphur. The largest pieces of 

 ore are selected for the first layer, leaving interstices between them ; 

 the size of the lumps gradually diminishes as the height increases, 

 care being taken to form the walls of the morto with calcareous 

 stones, so as to insure a passage being maintained for the escape of 

 the liquefied sulphur. In adding the finest portions on the top, narrow 

 channels, about two feet apart, are left for the draught to carry the 

 heat down. The whole is covered with a layer of the refuse from 

 previous operations. This layer is more or less thick, according to 

 the state of the weather, because, the calcarone being built in the 

 open air, variations of temperature and wind influence the pi'ogress of 

 the operation ; consequently means have to be adopted to prevent an 

 undue access of air rendering the combustion too rapid. For instance, 

 during a sirocco (local hot wind) there is danger of the sulphur con- 

 tained in the ore lying at the side facing the wind being completely 

 converted into sulphurous acid, and thus lost. The employment of a 

 roofed shed would prevent much of the waste occasioned by climatic 

 causes. 



When the charging is completed, the morto is closed by a stone 

 slab, and tire is communicated to the mass by means of little bunches 

 of dried herbs, dipped in sulphur, which are thrust into the vertical 

 channels before mentioned. Some six or eight days afterward, a hole 

 is pierced in the top of the morto, by means of an iron rod ; later, a 



•1 





Fig. 2. 



second hole is made near the floor. By these two openings the sulphur 

 escapes, and is collected in wooden buckets (gravite), shaped like a 

 truncated cone, and holding about one hundred-weight of sulphur. 

 These buckets cost over two shillings, and serve only for three or four 

 castings without wanting repairs. The outflow of sulphur lasts for a 

 fortnight or a month. Commonly, the calcarone is left to itself when 

 once the mass has been ignited, but then the loss of sulphur is much 

 more serious. To insure good results, many precautions have to be ob- 

 served, mainly connected with the nice adjustment of the draught, so 



