234 



Dr Colquhoun on the Argillaceous Ore of Iron. 



(a.) From Crossbasket, about seven miles south-east from 

 Glasgow. Colour, light-greyish, or greenish-black. Fracture, 

 from fine-grained, even, to coarse-grained, uneven. Very easily 

 frangible ; soft ; easily scratched by the knife. Specific gra- 

 vity, taken in distilled water at the temperature of 60% 

 3.1793. 



This is the highest and also the least valuable of the Cross- 

 basket strata of ironstone, which are at present raised for the 

 use of the blast furnace. The thickness of the stratum is from 

 three to three and a-half inches. 



(b.) From Crossbasket. Colour, light greyish-black. Frac- 

 ture fine-grained, earthy, shghtly uneven. Kather tough. Not 

 particularly soft. Sp. gr. 3.3801. 



This ore is found at a distance of four feet under the pre- 

 ceding one. It constitutes a stratum of about nine inches 

 in thickness, and is esteemed the purest and the most valuable 

 of the Crossbasket ores. 



f C.J From Crossbasket. Colour, light greyish-black. Frac- 

 ture fine-grained, earthy, slightly uneven. Rather tough, 

 but more easily frangible, and softer than the last mentioned 

 ore. Sp. gr. 3.2699. The average thickness of the stratum 

 is from six to eight inches. 



(d.) From Crossbasket. Colour, brownish-black. Frac- 

 ture, earthy, fine-grained, uneven. Easily frangible and soft. 

 Sp. gr. 3.1175. This stratum of ironstone is situated next 

 under that from which the preceding specimen was taken, and 

 forms the lowest which is at present wrought at Crossbasket. 



