Dr Colquhoun (m the Argillaceous Ore of Iron. 2S5 



It varies in thickness from ten to fourteen inches. Both it 

 and the preceding ore are reckoned of good average quality. 

 This ore furnishes a curious instance of the capricious and 

 seemingly unaccountable alterations that are liable to take 

 place in every chemical manufacture whose fundamental prin- 

 ciples are little understood, and in none, perhaps, does this 

 happen more frequently than in the smelting of iron. Al- 

 though it forms the thickest of all the Crossbasket strata, and 

 therefore holds out powerful inducements in an economical 

 point of view to the iron-smelter, it was at one period regard- 

 ed at the Clyde Iron Works as an ironstone totally unfit for 

 the manufacture of good iron, and having once received an 

 unfavourable character, it was allowed to remain unworked 

 for a long course of years. It is only of late that its employ- 

 ment has been again resumed ; but, so far from being held in 

 low estimation, it is now considered to be little inferior in 

 quality to any of the Crossbasket ores, and is used very ex- 

 tensively in the blast furnace. 



Immediately above this stratum there is situated a bed of 

 schist, containing a regular stratification of very large nodules 

 of ironstone. Being extracted by the miner simultaneously 

 with the subjacent ore, they are used to a considerable extent 

 in the blast furnace, and are esteemed an ironstone of uncom- 

 monly fine quality. The black bituminous substance, which 

 will be mentioned hereafter as occurring occasionally in nodu- 

 lar ironstone, exists very generally distributed throughout this 

 stratification of balls. 



(e.) A specimen found in the neighbourhood of the Clyde 

 Iron Works, which are situated about four miles south-east 

 from Glasgow.* Its mineralogical details are the following : 

 Colour, pale, between broccoli-brown and clove-brown. Frac- 

 ture, rather fine-grained, uneven. Not particularly hard ; 

 easily scratched by the knife. Sp. gr. 3.1482. The thick- 



• I beg leave to take this opportunity of expressing how much I feel in- 

 debted to Colin Dunlop, Esq. the proprietor of this smelting establishment, 

 for the valuable information which he has communicated to me respecting 

 this ore and its metallurgic treatment, and for the liberal permission which 

 he gave me both to examine every process of art at the Clyde Iron Works, 

 and to make the freest use of the knowledge thereby acquired in the course 

 of the present memoir. 



