194 On the Component Parts of Iron-ftones. 



1. Iron-ftone that has clay for its chief component earth, 

 and this clay comparatively pure and free from fand. 



2. Iron-ftone poffefling lime for its chief mixture, and this 

 lime alfo comparatively deftitute of fand. 



3. Iron-ftone that unites clay and lime, containing large 

 proportions of filex ; hence, for dittin&ion's fake, may be de- 

 nominated filiceous iron-ftones. I (hall therefore, in naming 

 thcfe varieties, ufe the following terms as they are arranged 

 in iucccffion. Argillaceous, calcareous, and filiceous iron- 

 ftones. None of thefts earths exift fingly with the iron. All 

 iron-ftones contain a mixture of the three, in various propor- 

 tions ; from which arife the fuppofed variety of the qualities 

 of crude iron, which each refpe&ive ftone is faid to contain. 

 There are fome, however, which are compofed of nearly the 

 fame proportions of clay, lime, and filex ; and thefe com- 

 monly afford, when compared with themfelves, a fimilar 

 quality of crude iron. 



Nature, in the formation of thefe fecondary ores of iron, 

 has invariably impreffed characters upon them, eafily to be 

 developed : by which means their qualities, and the confe- 

 quent effects produced in the blaft-furnace, may be accu- 

 rately and diftinetly prejudged. The fouree of this informa- 

 tion is, the ftudy of the nature of the united earths ; by af- 

 certaining the quantity and proportion of which, we are 

 enabled to pronounce exactly upon the quality of the iron 

 likely to be obtained from the ore. We muft not, however, 

 confider thefe characleriftic features as a confequence of the 

 metal exifting of a variety of qualities; but, a priori, we 

 ought to confider, that, as a confequence of the nature and 

 proportions of the mixture, the iron will be called into exiii- 

 ence in a ftate more or lefs oxygenated or carbonated. 



When iron-ftones are faid to contain good or bad iron, the 

 exprefiion ought to be underftood, which by the bye is fel- 

 dom the cafe, only as a comparative aflertiou, confined to 

 local rules, and judged by certain fixed local ftandards; into 

 the account of which many things muft be taken, which are 

 frequentlj overlooked. At every iron-work, a certain pro- 

 portion 



