Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/291

 as long as these quarries remain accessible to us. For that higher class of sculpture on which the powers of genius are exerted, the proportion between the price of the wrought and unwrought article, (to use commercial phraseology) is so unequal, that no difference in the value of the raw material can compensate for even the most trivial defects in its quality. But there remains even in the class of the fine arts a great number of uses to which the marble of Glen Tilt might with advantage be applied. Such are all those works in architectural decoration, in which absolute whiteness and uniformity of colour, are not only unnecessary, but from their dazzling effect even injurious. The subdued tone and slight air of antiquity given to this marble by its stained and unequal colour would in these works render it of the greatest use. Its durability for the purposes of interior architecture must also be equal to that of Carrara, although there is little doubt that when exposed to the action of the weather it would like the Pentelic be liable to corrosion in those parts which abound in mica.

Besides mica, steatite and noble serpentine are found mixed with the white marble. The colours of these substances offer various gradations from bright yellow down to the darkest sap green. It is by these admixtures that the green and white marbles which form by far the largest portion of these beds are produced. The colours are so variously mixed, blended, and dispersed throughout the stone that numerous varieties are the result; and these are further increased by the occasional presence of dark lead blue. This mixture of serpentine with marble is by no means uncommon in Scotland. On the contrary it may be said that all the white marbles found in this country contain it in a greater or less It is common in the white marble of Sky and in that of Balahulish. In that of Assynt it is more rare, but it occurs also abundantly in a