The rocks which are destitute of mica, or in which the mica lies irregularly, or in which it is altogether absent, I shall call Compact Crystallines. The rocks in which the mica lies regularly I shall call Slaty Crystallines.
§ 14. 1st. Compact Crystallines.--Under this head are embraced the large group of the granites, syenites, and porphyries,--rocks which all agree in the following particulars:--
Their first characteristic. _Speckledness._
A. Variety of color.--The method of their composition out of different substances necessitates their being all more or less spotted or dashed with various colors; there being generally a prevalent ground color, with other subordinate hues broken over it, forming, for the most part, tones of silver grey, of warm but subdued red, or purple. Now, there is in this a very marvellous provision for the beauty of the central ranges. Other rocks, placed lower among the hills, receive color upon their surfaces from all kinds of minute vegetation; but these higher and more exposed rocks are liable to be in many parts barren; and the wild forms into which they are thrown necessitate their being often freshly broken, so as to bring their pure color, untempered in anywise, frankly into sight. Hence it is appointed that this color shall not be raw or monotonous, but composed--as all beautiful color must be composed--by mingling of many hues in one. Not that there is any aim at _attractive_ beauty in these rocks; they are intended to constitute solemn and desolate scenes; and there is nothing delicately or variously disposed in their colors. Such beauty would have been inconsistent with their expression of power and terror, and it is reserved for the marbles and other rocks of inferior office. But their color is grave and perfect; closely resembling, in many cases, the sort of hue reached by cross-chequering in the ground of fourteenth-century manuscripts, and peculiarly calculated for distant effects of light; being, for the most part, slightly warm in tone, so as to receive with full advantage the red and orange rays of sunlight. This warmth is almost always farther aided by a glowing orange color, derived from the decomposition of the iron which, though in small quantity, usually is an essential element in them: the orange hue forms itself in unequal veins and spots upon the surfaces which have been long exposed, more or less darkening them; and a very minute black lichen,--so minute as to look almost like spots of dark paint,--a little opposed and warmed by the golden Lichen geographicus, still farther subdues the paler hues of the highest granite rocks. Now, when a surface of this kind is removed to a distance of four or five miles, and seen under warm light through soft air, the orange becomes russet, more or less inclining to pure red, according to the power of the rays: but the black of the lichen becomes pure dark blue; and the result of their combination is that peculiar reddish purple which is so strikingly the characteristic of the rocks of the higher Alps. Most of the travellers who have seen the Valley of Chamouni carry away a strong impression that its upper precipices are of red rock. But they are, without exception, of a whitish grey, toned and raised by this united operation of the iron, the lichen, and the light.