ON SPARRY IKON ORES« ^|^ 



•ometiraes there may be 12 per cent of either in the raw ore, manganese 

 and at others there is scarcely any. ^*^ magnesia. 



From the results of his analyses Mr. Descotils concludes, Never a maxi- 

 that a high proportion of one excludes a high proportion "^^^*^^^^^' 

 of the other, without the absence of the one necessarily in- 

 dicating" the presence of the other; so that the iron, when 

 brought to the state of red oxide, always amounts to 60 per 

 cent at least. 



Hence Mr. Descotils explains what takes place in the Ca- Cataloniaa 

 talonian forges, where the different species of ore are treated '^'^^^' 

 according to the nature, number, and quantity of the prin- 

 ciples they contain. He points out the method, that each 

 requires, and the product they afford, according as the ope- 

 ration is conducted. Sometimes it is cast steel, at others steel from th«. 



malleable iron, or some mixture of the two. On this occa- ^^'-' Pyreaoau 



ore. 

 fion he expresses his surprise, that no one has yet thought of 



establishing a manufactory of cast steel in the Pyrenees. 



He thinks justly, that all rich iron ores, which contain btit Richores» 

 few earthy parts, such as those of the island of Elba, might 

 t)e fused with advantage in the Catalonian method. 



It follows evidently from the experiments of Mr. Descotils, General d©* 

 that certain kinds of sparry ores owe their infusibility to the Auction** 

 presence of a large quantity of magnesia: and that the prin- 

 cipal object of the exposure of these ores to the air and rain, 

 either before or after roasting, is to separate the magnesia, 

 and render them fusible. The various experiments we have 

 witnessed, and the results of which we have seen, leave us no 

 -doubt on this head: since on the one hand the ores in which 

 there is no magnesia are easy of fusion, and those which con- 

 tain a certain proportion are wholly infusible; while on the 

 other the addition of magnesia to fusible, ores divests them of 

 this property, and infusible ores, when their magnesia is ab- 

 stracted from them, become fusible. 



From the observations of Mr. Descotils it farther follows, 

 that there is no external character, by which we can distin- 

 guish whether a sparry iron ore be fusible or not: but he has 

 pointed out chemical means of determining their nature, 

 which are easy to put in practice. 



Hence we are of opinion, that Mr. Descotils has thrown 

 much liglkt on the working of sparry iron ores; and that, as 



big 



