$36 Dr Colquhoun on the Argillaceous Ore of Iron* 



ness of the stratum is about 2J inches. It is considered at the 

 works to be an ore of very inferior quality, and is seldon^ 

 smelted. 



Immediately above this ore there is situated a bed of schist, 

 which contains an immense number of petrifactions of different 

 kinds of bivalve shells. They consist of a very 'pure irorir- 

 stone, resembling in appearance the subjacent band (f.) 

 Their forms are remarkably perfect, and they contain no vi- 

 sible remains of the original shell. ^ 



(jT.) An ore lying under the last mentioned stratum, and in 

 close contact with it. Colour between yellowish-grey and hair- 

 brown. Fracture, fine-grained, earthy, even. Rather hard ; 

 scratched with some difficulty by the knife. Sp. gr. 3.2109. 

 The stratum to which it belongs is situated above the splint 

 tjoal, with the intervention of only four inches of schist, and 

 both minerals are therefore worked out together with great 

 advantage to the smelter. It is the most valuable ore in all 

 the fields around Glasgow, except that called the Black Iron- 

 stone, which is at present smelted at the Clyde iron works. 

 The thickness of the stratum is between one and a half and two 

 inches. 



(g.) This specimen was procured from Easterhouse, near 

 the line of the Monkland Canal, and about six miles east from 

 Glasgow. Colour, clove-brown. Fracture, fine-grained, rather 

 uneven. Somewhat tough and hard, but easily scratched by 

 the knife. Sp, gr. 3.3109. 



This ore exists in precisely the same relative situation with 

 regard to all the other accompanying minerals, as the two ores 

 from Clyde Iron Works which have just been described ; and 

 wherever it makes its appearance it seems to have been pro- 

 duced by the coalescence of these two strata. This compound 

 stratum has always a uniform texture and composition through- 

 out. Its average thickness is two and a half to three inches. 

 It is used pretty extensively in the blast furnace, and is esteem- 

 ed an ore of good average quality. 



(h.) From the neighbourhood of Airdrie, about ten miles 

 east from Glasgow. Colour, clove-brown, the intensity of the 

 shade varying considerably in streaks which are parallel to the 

 direction of the stratum. When reduced to powder the co- 



