110 Dr. Mac Culloch's Sketch of the 



tains no earth but lime, is of unusual specific gravity and hardness. 

 It is incapable of being polished, a circumstance, it is true, of no 

 consequence in statuary, since the polish only gives a false light to 

 the surface and is not admitted of in modern sculpture ; but it 

 labours under the concomitant disadvantage of want of trans- 

 parency, producing nearly the same dead effect and dry outline 

 as is seen in a plaster cast, a fault in itself sufficient to prevent 

 it from ever being adopted as a good material in the arts : its ex- 

 treme hardness also renders it very expensive to work. 



The marble of Sky, the more immediate object of this dis- 

 cussion, is of a pure white colour, and appears sufficiently extensive 

 and continuous to be capable of yielding large blocks. The purity of 

 its colour is seldom contaminated ; its fracture is granular and 

 splintery, and its texture fine, less fine than that of lona, but more 

 so than that of Assynt : its compactness, hardness, and gravity, are 

 greater than those of the marble of Carrara, which it in fact re- 

 sembles in little else than colour. It is apparently well fitted for 

 all purposes of sculpture, as it can be wrought in any direction, 

 and has sufficient transparency, while at the same time it assumes 

 even a better polish than is required for statuary. With these good 

 qualities, however, is combined an uncertainty arising from its un- 

 equal hardness. While some parts of the stone are nearly as easy 

 to work as that of Carrara, many other specimens turn out so 

 hard as to add a charge of near 50 per cent, to the cost of work- 

 ing : this appears to arise from the influence of the syenitic and 

 trap veins which traverse it, as I have before mentioned, but which 

 however produce no change in its chemical composition, nor any 

 other effect than that of induration. This addition of price to the 

 current charge of working is sufficient in the harder specimens to 

 counterbalance in a great degree the superior cheapness of the ma- 



