32B' Manufacture of Suljihat of Iron, 



and copper with an excess of acid. During the process of 

 evaporation a leaden vessel, having its sides perforated and 

 containing fragments of old iron is suspended in the liquor. 

 The iron at the same time that it neutralizes the excess of 

 acid, decomposes the sulphate of copper and the copper is 

 precipitated in the form of a fine powder which the work- 

 men call " copper mud." In a conversation with Profes- 

 sor Cleaveland upon this subject he observed, that he could 

 not conceive why the copper did not form a pellicle upon the 

 iron. I think its detachment is referable to the constant 

 and active operation of the acid in the hot liquor, removing 

 the copper as fast as it is deposited. Hydrogen gas which 

 I collected in tumblers and burned, is evolved during 

 the solution of the metalhc iron in the acid liquor. When 

 the liquor is first heated it becomes turbid with some earthy 

 material, probably alumine. 



After th^ liquor has been sufficiently evaporated it is 

 drawn off into cisterns to crystalize. Branches of trees are 

 put into them as a nucleus for the crystals. When the 

 crystalization has proceeded as far as it will go, the remain- 

 ing fluid is drawn off, and returned to the evaporating v^.es- 

 sels. The cistern remains lined several inches in thickness 

 with crystals, like a geode. The branches have a fine crop 

 of foliage and fruit composed of beautiful green crystals. 

 The crystals are very large and perfect, presenting numer- 

 ous brilliant facets which are often several inches broad. I 

 obtained some which were perfect four sided prisms with a 

 rhombic base six inches in length and half an inch broad. 



Every thing about this mineral manufactory is curiously 

 reddened with iron rust. When a dry day succeeds a rain 

 or a shower, the whole mine becomes covered with a white 

 crystalline efflorescence like a hoar frost, and the rain water 

 which runs down into the cavities of the mine becomes so 

 strong a solution as to crystalize. Wherever the solution 

 dribbles from the rocks, or leaks from the cisterns, large 

 stalactites are formed so precisely like icicles that they 

 would not be distinguished from them were it not for their 

 green colour. These stalactites are very numerous at some 

 seasons and present a very beautiful spectacle. 



An ingenious method has been contrived to catch the 

 wash of the whole mine. There has been cut in the com- 

 pact ore, quite across the lower edge of the mine, a chan- 



