Chinese process for making Sheet Lead. 391 



to one of the primitive planes, viz. that which is the least 

 aasy to obtain by cleavage. Several of the forms greatly 

 resemble some of the varieties of feldspar, being composed 

 of the sameiiumber of planes disposed in the same manner, 

 and it is only by using the Goniometer that the difference 

 can be perceived. Notwithstanding this great anology, Mr. 

 Levy believes that the forms of the two substances are in- 

 compatible. He considers the primitive of feldspar to be 

 an oblique rhombic prism, and not a doubly oblique prism, 

 as it had been supposed by Haiiy, and he takes for the prim- 

 itive of Cleavelandite a doubly oblique prism. The crys- 

 tals of Cleavelandite are generally white, sometimes yellow- 

 ish and reddish. They are transparent, sometimes translu- 

 cent and opaque, and have a certain brilliancy which does not 

 belong to Feldspar. Both substances are often found upon 

 the same specimen, and sometimes both in large and well 

 defined crystals. The localities of Cleavelandite are very 

 numerous, and this substance seems likely to become one of 

 the most important both in mineralogy and geology. All 

 the rocks of which feldspar is considered as a component 

 part, must be re-examined to separate those which really 

 contain feldspar, from those which contain Cleavelandite. 

 The localities derived from Mr. Turner's collection are the 

 following : Dauphiny, St. Gothard, Tyrol, Piedmont, Bave- 

 no, Elba, Vesuvius, Saxony, Sweden, Norway, Siberia, 

 Greenland, United States, and Rio Janeiro. 



An. Philos. JVov. 1 823. 



27. Chinese process for making sheet lead. — The reduc- 

 tion of lead into thin sheets, is done by two workmen, one 

 seated on the ground, having before him a large flat stone, 

 very smooth, and holding in his hand another flat stone, a 

 kind of muller; along side is a furnace in which is placed a 

 crucible filled with lead. A second workman pours upon 

 the stone, a quantity proportioned to the size and thickness 

 of the intended sheet, and the other pressing his muller for- 

 cibly upon it, produces a leaf which is very thin, and of an 

 equal thickness throughout. It is immediately removed and 

 the operation repeated with extraordinary rapidity. When 

 a certain number of sheets are obtained, they trim the bor- 

 ders which are always ragged, and tie them together. 



