inches: some are seen also of an elongated form; but the layers are always concentric, and composed of parts converging to the centre, or towards the axis of the mass. Sometimes these layers, although concentric, are undulating or festooned. These balls, both the large and small, often intermix and arrange themselves in strange forms; and nevertheless the whole is disposed in beds pretty regular, a little inclined, rising to the north or north-east.

"The spar which forms these balls, is of honey-yellow, or translucid yellowish white; and the grain is very brilliant. The interstices of the balls are filled with a less dense matter, often cellular and of a coarser tissue, but the nature of which is essentially the same.

"One cannot but observe in these forms the work of crystallisation; stalactites and geods are seen to present similar structures; but an entire mountain, composed of an assemblage of these crystallisations, is a most extraordinary phenomenon."

• Sauss. § 1478.

NOME XIX. BARYTIC ROCK.

Mr. Kirwan informs us, that Hoepfner discovered a whole mountain in Swisserland, composed of quartz, barytes, and mica partly compounded with shorl. Mr. Kirwan calls this kind of barytes, baroselenite; because it resembles selenite, or gypsum crystallised in plates. It is the plane, laminar, heavy spar of Werner, in which the most common colours are white and red. In the curious rock here mentioned, the barytes was of a flesh red colour; but it must not be forgotten that Hoepfner's observations and analyses are not of the first authority; and his barytes may be found to be a felspar.

In the mineralogy of the department of the Loire, there is the following account of a singular rock near Ambierle, a village near three leagues N. W. of Roanne*.

"There is there seen a rock, situated between two little valleys, on the eastern side of the hill. This rock, which separates these two valleys, is a disordered mass, composed of fluor and barytes, sometimes mixed, sometimes in separate and distinct parts, but always in intimate contact, and

Journal des Mines, iv. 127, by Passinges.

traversed by some veins of quartz. The fluor is of various colours: green, violet, and reddish; yielding much phosphorescence when thrown on hot iron, as well as a spathose acid gas, very acrid and corrosive, when it is heated with vitriolic acid. The barytes is white, with a slight tinge of red, very pure, and disposed in large plates. It is sometimes crossed with veins of a beautiful pitch-stone, of a deep yellow, a little transparent, but sometimes opake, and resembling yellow resin.

"The texture of this pitch-stone is rather loose, and it seldom strikes fire with steel; but in its fracture it shows the conchoidal form, as well as the convolved streaks of silex; while some, in a state of decomposition, leave a lilac coloured earth, which cleaves to the tongue. It appears that it is coloured by iron, for there appear, in some parts of this stone, grains of that metal, which have given more intensity to the colour of the pitch-stone in the adjacent parts.

"On examining some of the fluors, it may be observed that there have been successively deposited new layers of the same fluor, and of quartz of different colours, till the cavity, in which the first crystals were formed, was filled up. This frequent mixture of different substances forms veins in zigzag; because they fol

lowed in their deposition the unequal angles of the cubes, which served them as a base. Some of these fluors have shown indications of the oxyd of cobalt, others of manganese in stalagmites. Only one piece of fluor has been found traversed by the same pitch-stone: there are also found, but rarely, small cavities which contain little crystals of fluor, barytes, and quartz.

"It may be judged by the quantity of fragments scattered around this rock, and in the surrounding vineyards, that it has been of a far greater height, and that it has been injured and shattered from many causes, but especially the cultivation of the neighbouring vineyards; there are even large open slits, which show that it has been shaken. It has even been attempted to make mill-stones with the barytes, of which there are large masses, but the attempt did not succeed. All these fragments display much more quartz, mingled with the fluor and barytes, than the rock itself; which, nevertheless, may be said to form a kind of pudding-stone, as presenting adherent mixtures of various kinds.

"The environs of this remarkable hill show, in the hollow roads, veins of barytes amidst fluor. The rocks of the adjacent mountain are of primitive grey granite, consisting of felspar, quartz, and mica. It is rather soft, but is used for the

supports and traverses of doors and windows, resisting the air a considerable time. It is to be presumed that mines may be discovered in this district, though nothing in that way has been attempted. Some cubic pyrites, yellow or black on the surface, give no strong hope in that respect."

Some important rocks must now be considered, which are not only anomalous in their structure, as the preceding; but of which the whole mass forms a deviation from the usual order of nature. Such are, as above mentioned, the Saline, Bituminous, Sulphuric, and Iron Rocks.

NOME XX. SALINE ROCKS.

The most remarkable of these exist in Spain and Africa. The latter saline hill can only be said to have been observed; but those of Spain have been described by Bowles, in his natural history of that country*. The first is in Spanish Navarre, between Caparoso and the river Ebro, in a chain of hills which extend from east to west.

* See the French translation, by Viscount Flavigny, Paris 1776, 8vo. p. 376, 406.