Mineralogy of Sky. 1G7 



alternate with the limestone strata on the Broadford side, and in 

 the inferior solidity and thickness of the calcareous beds ; while at 

 the same time the harder schist, which divides them on the south- 

 western shore, is absent, the one appearing to be a substitute for 

 the other. The shale is a mixture of black clay, sand, and mica, 

 thickly and imperfectly fissile, and the sandstone which is of dif- 

 ferent colours, but generally brownish, contains much clay and 

 calcareous earrh, the organic remains being found in each of these 

 beds just as they are in the limestone. 



The interruptions, to which I have here alluded, that prevent 

 us from tracing the limestone over the hills that bound the southern 

 side of Strath, arise partly from the boggy and covered nature of 

 the ground, and partly from the intrusion of a hill of syenite, 

 which extends far from the portion formerly noticed, towards 

 Broadford, and which can in many places be distinctly traced 

 overlying the limestone, shale, or sandstone, as either of these 

 happens to be present at the point where the contact is exposed. 

 There is no satisfactory evidence to be procured here of that change 

 from the stratified to the unstratified limestone which I have de- 

 scribed in the original paper, since there is no situation, where the 

 contact of the two can be precisely traced. Yet there is even here 

 sufficient evidence to give rise to such a suspicion, and more than 

 enough to confirm the observations formerly recorded, and to 

 justify the conclusions deduced from them. To enter into further 

 details on this subject would now be superfluous, as the feebler 

 evidence is of little value where the stronger has preceded. I shall 

 only add, that beds of ordinary quartz are in one place found 

 regularly interstratified with the marble limestone, as if the power 

 which had converted the common limestone into this one, had also 

 changed the sandstone into quartz : and that many gradations by 



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