

1853.] Report on the Geological Structure of the Salt Range. 337 



with an efflorescence of alum containing a large proportion of sul- 

 phate of iron or green vitriol derived from the mutual reaction of the 

 clay and iren pyrites in the shales, which from containing thin films 

 of coal are admirably adapted for alum manufacture. Close to the 

 kiln, and on a level a little below its base, there is a baked clay vat 

 12 feet square by 1| feet deep. Into this a portion of the burnt 

 shale is thrown and treated for several hours with water which 

 rapidly acquires a dark brown colour. When a saturated solution 

 of the soluble matter in the shale is obtained, it is drawn off from 

 the vat by an aperture in its side (which during the lixiviation of 

 the shale is stopped by a plug) into another vat of similar size, but 

 on a lower level. Here the crude alum liquor is allowed to deposit 

 any mud which it may contain, and is then run off into a third but 

 smaller vat on a still lower level, when it is again allowed to deposit 

 any remaining impurity. From this it is transferred into an iron 

 evaporating pan or "kurrah" where it is rapidly boiled and mixed 

 with a brownish impure salt called " Jumsan" from which it derives 

 the alkali necessary to convert the crude alum into an alum of com- 

 merce. When a proper quantity of this has been added, which is 

 judged of from the apparance of the liquid, the whole is allowed to 

 settle and the clear brown alum solution removed into vats about 

 nine feet long 5| broad and about 1^ feet deep, a series of which 

 are arranged beneath a shed close to the evaporating pan. In these 

 the solution, which is concentrated to a point a little short of that 

 of crystallization, is allowed slowly to crystallize for several days. 

 During that time small alum crystals are formed of a slightly pink 

 colour devoid from the impure mother liquor which contains a quan- 

 tity of chloride and sulphate of iron. When a considerable crop of 

 alum has separated, the crystals are removed from the vat, slightly 

 washed with cold water on a sirkee frame, aud allowed to dry. 

 These are afterwards fused in an iron pan, in their own water of 

 crystallization and when in a fluid state are removed into large coni- 

 cal earthen jars, one foot eight inches deep, the same breadth at the 

 shoulder, and six inches wide at the mouth, where for eight or ten 

 days the alum is allowed to crystallize. At the end of this period a 

 hole is made in the mass of alum, which is generally hollow in its 

 interior, the gurrah inverted, and the uncrystallized alum liquor 



