72 Scientific Notices — Mineralogy. [July, 



Carbon 55-30 



Oxygen 36*50 



Hydrogen 8*20 



100-00 



Or very nearly, of 4 atoms of carbon, 2 of oxygen, and 3 of 

 hydrogen. — (Bibliotheque Universelle, Oct. 1823.) 



3. Argillaceous Iron Ore. 



The analysis of this ore, given in the last number of the Annals, 

 was incorrectly stated. The reader will perceive that the quan- 

 tities of lime and carbonaceous matter, having been obtained 

 from 200 grains of the ore, should have been divided by 2; and 

 a small quantity of alumina separated from the precipitated 

 oxide of iron being added, the composition will be nearly as 

 follows, and as it will be found stated in Phillips's Mineralogy, 

 p. 237, viz. 



Protoxide of iron, with a trace of man- 

 ganese 43*26 



Carbonic acid 29*30 



Silica and alumina 20*78 



Carbonaceous matter 2*67 



Lime 1*89 



Moisture 1*00 



Loss M0 



100*00 R. P. 



4. Aberthaw Limestone. 



This limestone, which is highly esteemed for the goodness of 

 the lime which it yields, I have found to consist'of 



Carbonate of lime 86*17 



Alumina 7*10 



Silica •. 3*40 



Carbonaceous matter 1*67 



Moisture 1*00 



Oxide of iron 0*66 



100*00 R. P. 

 Mineralogy. 



5. Composition of Tourmaline. 



M. Gmelin, who has devoted a good deal of attention to the 

 analysis of this mineral, deduces the following conclusions from 

 his researches. All the tourmalines hitherto examined by him 

 contain from two to six per cent, of boracic acid, which appears 

 to be quite an essential ingredient. All of them contain also 



