92 Dr Colquhoiin 07i the Argillaceous Ore of Iron. 



On comparing specimens from each of these strata, their cha- 

 racters proved to be as follows. 



The limestone belonging to the upper stratum had a black- 

 ish grey colour and broke with a rather fine-grained, earthy, 

 imeven fracture. The lustre of the fractured surface was al- 

 most dull. It was not altogether free from an intermixture 

 of small particles of iron pyrites, and contained dispersed 

 through its mass, a few remains of shells. On subjecting it 

 to analysis, it was found composed of 



101.08 



The limestone of the lower stratum was of a brownish grey 

 colour, and its fracture was fine-grained, splintery, and un- 

 even. Its structure was more distinctly crystalline than that 

 of the other, and its fractured surface had a glimmering lustre. 

 It also contained traces of iron pyrites. On analysis, its con- 

 stituents were found to be 



100.46 

 It is evident, from comparing these two analyses, that the 



