4-8 Sketch of the latest Improvements [JaJ.% 



Its constituents are as follows : — 



Lead 82-6923 



Carbonic acid 3*8462 



Oxide of iron and lime .... 0*4808 

 Copper, a trace. 



Silica mixed with iron .... 2*4039 



Oxygen 10-.5768 



100*0000 



14. Supposed Native Minium from Kail, i>i the Roer Depart- 

 ment. — I am not sure whether this be the native minium of Mr. 

 Smithson, as 1 have not his dissertation at hand. Its characters are 

 as follows : — 



Colour, brownish-red. Amorphous. 



Fracture fine-grained, uneven. 



External lustre, dull ; internal, glimmering. 



Opake ; soft ; easily frangible ; sp. gravity, 4-000. 



Dr. John found its constituents as follows : — 



Lead 44*15 



Carbonic acid 10*00 



Water 4*00 



Lime and oxide of iron 0*50 



T 1 ui .* rSilica 29*00 



Insoluble matter Kj^^i^a 5.25 



composed of . . ^^^.^^ ^^ .^^^ 3.^^^ 



Oxygen 4*10 



100*00 



By comparing this analysis \vith the preceding, it is obvious that 

 the oxide in this mineral is not the red, but the yellow oxide of 

 lead, and that it owes its red colour to the oxide of iron which it 

 contains. The proportion of oxygen is obviously over-rated in both 

 analyses. 



15. Spinell. — A specimen of spinell, from Oker, in Suderman- 

 land, in Sweden, analysed by Berzelius, gave the following consti- 

 tuents : — 



Alumina 72*25 



Silica 5*48 



Magnesia 14*63 



Oxide of iron 4*26 



Water '. 1*83 



Loss 1 '55 



100*00 



16. Red SiUcio7/s Ore of Manganese. — A specimen of tliis ore 

 from Longbansbyttan, in Wcrnieland, in Sweden, analysed by 

 Berzelius, was composed of 



