78 Dr Colquhoun on the Argillaceous Ore of Iron. 



with the sand; ninth, the bitumino-argillaceous ; and tenth, 

 the bitumino-calcareous, — terms which sufficiently expdain 

 their own meaning, in conformity with the foregoing nomen- 

 clature. To the eleventh and last class, belong the sulphure- 

 ous and phosphorized ores, or those whose constitution, what- 

 ever it may be in other respects, is contaminated by the presence 

 of sulphur or phosphorus. 



These are the leading classes into which the ore of iron may 

 be divided when it is regarded as a subject of manufacture. 

 And as we have already endeavoured to give a mineralogical 

 and geological account of this ore, we shall not dwell \ong(*r 

 upon the first of the crude materials used in the smelting of 

 iron, but shall proceed to examine the nature of those which 

 remain. These are fuel and limestone. 



Section 2. — On Fuel and Fluxes. 

 . After examining the nature of the ironstone, which is the sub- 

 ject, and the basis of the iron smelter's manufacture, the class of 

 crude materials still remaining to be considered, consists of those 

 with which he treats the ore, for the purpose of detaching its me- 

 tallic ingredient. This class is composed of fuel and fluxes. By 

 the application of the first of these, the oxide contained by the 

 ore is reduced to the metallic state. But this process of re- 

 duction constitutes only a single stage in the course of the 

 ironsmelter's operations. The iron thereby developed re- 

 mains dispersed, in small particles, throughout the substance 

 of the ore ; and even the intense heat of the blast-furnace 

 would prove inadequate to combine these particles together, 

 and extricate the solid metal in a united state, unless some 

 thing more than mere fuel were employed. It is necessary to 

 bring the earthy matter, with which the metallic particles are 

 intimately intermixed, to a state of thin fusion and liquidity, 

 before they can associate into small masses, and then, by their 

 superior specific gravity, subside together to the bottom of the 

 furnace. But as there is generally one earthy ingredient, 

 the amount of which is greatly predominant over the others in 

 each ore, and as all the simple earths, and even the greater 

 number of their binary mixtures are infusible by the heat of 

 the blast-furnace, it is necessary for the smelter to call in the 

 lud of some other agent for the purpose of reducing them to 



