213 Anahjsb of the magneficul Pyrites. 



Ill the mineral kingdom a great variety of substances, 

 and even some ol" the gems, exert a feeble degree ut" attrac- 

 tion on the magnetic needle, and sometimes also acquire a 

 slight degree ot polarit)'*; but, as this wonderful property 

 has only been observed conspicuously powerful in one spe- 

 cies of iron ore, this has been always emphatically called 

 the magnet \y and is said to consist of metallic iron com- 

 bined wilh from 10 to 20 percent, of oxygen. 



From the facts, however, which have been recently stated, 

 we now find that there is another natural substance, appa- 

 rently very different from the magnet in chemical composi^ 

 tion, but nevertheless approachmg very nearly to it in 

 power, which is found in several parts of our globe, and 

 particularly in a province of this kingdom, where it consti- 

 tutes a vein, running north and south, of considerable ex- 

 tent, and several yards in width and thickness. 



From the experiments also which have been made on the 

 artificial preparation of this substance, we find that it is 

 capable of receiving the magnetic properties when the pro- 

 portion of sulphur amounts to 37 per cent., and is still 

 pow erfully attracted when •: much larger (juantity of sulphur 

 IS present. There is, however, some point at which all 

 these eft'ccts cease; and this point appears to be when the 

 sulphur is in some proportion between 45 or 46 and 52 per 

 cent. The preceding experiments have also proved, that 

 iron, when combined witli phosphorus, likewise possesses 

 the power of becoming a magnet to a verv remarkable de- 

 gree ; and, by the similarity, in this respect, of the carburet 

 or iron called steel, to the above sulphuret and phosphuret, 

 a very remarkable analogy is established between the effects 

 produced on iron by carbon, sulphur, and phospliorus. 



Carbon, when combined in a very large proportion with 

 iron, forms the carburet of that metal called plumbago ; a 

 brittle substance, insoluble in muriatic acid, and destitute 

 of magnctical properties. But smaller proportions of car- 

 bon, with the same metal, constitute the various carburets 

 included bctv.-een black cast iron and soft cast steel :J; bodies 



which 



* Cavallo on Magnetism, p. 73. 



t In a future piper it is my incenr'on to give an account of some com- 

 parative analyses or the varieties of this substance. 



+ " When (he carbon uxcceHs, the compound is carburet of iron, or 

 plumbago; when the ir >n exceeds, ihe compound is steel, or cast iron, 

 jii various states, accordinjj to the proportion. All these compounds may 

 oe considered ds subcarbureis of iron." — Thomson's System of Chemis- 

 try, vol. i. p 1^15. 



Mr. Muilict, m the following table, exhibits the proportion of char- 



coai 



