various prrts of Scotland, 415^ 



map in the possession of the Society, founded on the general opinion 

 of the mineralogists of Scotland, calls it a floetz limestone. 



A very cursory survey of it is sufficient to show, that it consists 

 of irregular and broken fragments of beds disposed in every possible 

 position. Occasionally it is flat, but is now and then elevated at a 

 small angle, and often appears as if it consisted of strata perfectly 

 vertical. Almost every where it is disturbed and contorted to 

 a great degree. The beds are easily traced in several places^ 

 where quarries have been dug, or mines wrought ; and in many 

 others the inclination of the soil and the action of water, have laid 

 the edges bare for some hundreds of yards together. The perfect 

 similarity of its disposition to that of the limestone which accom- 

 panies clay slate all over the Highlands of Scotland, and more par- 

 ticularly to that of the island of Lismore, would suffice to determine 

 its true character, even without the detail of specimens. There are 

 two predominant varieties of it. Of these, one is dark blue, and 

 the other greyish white. They are both compact, and hard, but 

 the aspect of the whiter varieties is more crystalline than that of 

 the dark, which indeed often possess a merely earthy and granular 

 appearance.. In many places the blue varieties, where most crystal- 

 line, are traversed by numerous veins of a white colour, producing 

 an ornamental marble worthy of attention. 



. The blue varieties of this limestone appear to be deposited in con- 

 tact with clay slate, the white on the contrary, which are much more 

 rare, are found in contact with a micaceous slate. 



When the blue variety approaches the clay slate, it first assumes a. 

 schistose fracture. Shortly after it appears penetrated with delicate 

 laminse of straight or undulating silky schistus, which by degrees 

 increase in number, and at length so predominate, that it is only 

 by examining the cross fracture, and even with some care, that the 



