beautiful crystals of Zeolite with Chalcedony, Calc-spar, Arragonite, etc.

42 Gallinace (Syn. Trachylite, Vitreous Basalt).-Vitreous or semi-vitreous masses, sometimes stratified, of the color of pitch, bluish or brownish, having the appearance of earth or enamel, but less durable than Feldspar, easily fusible to a colorless bead; speckled with black and often scoriaceous. Density, 2.56 to 2.7. Silica, 56% in the Trachylite of Hanover.

Scoriaceous Basalts; Basaltic lava.

Stratiform Scoria. The exterior crust as well as the lower portion, which was the first to be ejected, often has a scoriaceous or porous texture, homogeneous or porphyritic, and more or less vitreous. The blocks ejected during the eruption have irregular forms. They are contorted, and divided into cells by partitions (Cloisonées).

Some by projection through the air, have, by reason of a rotatory motion, acquired an ellipsoidal form, with elongated and twisted extremities (volcanic bombs). They are generally red on the exterior and rich in Peridot, the Iron of which is generally in the state of peroxide.

Lapilli Scoriæ in small fragments, which have fallen in showers about the crater.

Basaltic Cinders.-Pulverulent scoriæ. Those of the eruption of 1843, were of a clear gray color, and contained 46.31 % of Silica; 16.85 Alumina; 9.85 Ferric peroxide; 4.43 Ferric oxide; 10.28 Lime; 5.44 Magnesia; 1.41 Potassa; 3.34 Soda; 2.21 Sulphuric acid; 0.52 of Hydrochloric acid, Ammonia and Gypsum.

Basaltic Scoriæ, in layers or in the state of lapilli or cinders, more or less decomposed, are employed in the manufacture of hydraulic cement under the name of Puozzolani. Ex. The catacombs of Rome are excavated in this rock. Laterite is a rock of this class and forms a deposit between dikes of Basalt in the West Indies.

43. Nephelinites.-Rocks with a compact or granular tex

Gallinalool En

ture-all having the appearance of Basalts and differing only by the substitution of Nepheline for Feldspar.

Nepheline is found in six-sided prisms and is recognized by its greasy lustre, by its color, which is yellowish-white, sometimes greenish or reddish; its fusibility before the blow-pipe; and its gelatinous deposit in hydrochloric acid which finally dissolves entirely.

Varieties: N. Granular; N. with fine grains; N. compact; N. with Amphigene (passing to Amphigenites). A great number of the lavas of Lake Laach enclose in their cavities crystals of Nepheline, Haüyne and Zircon.

44. Amphigenites.-Compact rocks, often porous, of a clear or deep gray or reddish color. These are Basalts in which the Feldspar is replaced by Amphigene. Throughout the paste are distributed grayish-white crystals, either of Amphigene in trapezohedrons or small crystals of Augite.

Amphigene is easily recognized by its almost spherical form and its complete decomposition, with a deposit of Silica in hydrochloric acid; and its fusibility before the blow-pipe.

The prisms of Augite are small and of a grayish or greenish color. Amphigenites almost always enclose more or less Nepheline and often Haüyne.

Accidental minerals: Breislakite; Melilite; Melanite; Mica; Sodalite; Copper Chloride.

Varieties: Compact Amphigenite (few apparent crystals); Porphyroidal Amphigenites or Leucitophyre; Scoriaceous Amphigenites, Lavas with Amphigenite (Vesuvius).

In certain Lavas of Vesuvius, Amphigene and Sanidine have been distinguished as essential elements.

45. Hauynophyre.-Lavas of a deep gray or blackish color which are allied to the basaltic lavas, only the Feldspar is replaced in part by vitreous Haüyne in rhombohedral dodecahedrons, ordinarily blue, sometimes white by alteration.

46. Augitic Rocks.-Described by Sterry Hunt of Chatham, Canada. Rock formed of granular Augite.

Соссо

Accessory elements: Tourmaline; Amphibole, etc. lite. Masses formed of grains of Pyroxene, sometimes white (having a base of Lime and Magnesia), sometimes green or blackish (base of Lime, Magnesia and Iron).

47. Eukrite.-Granular aggregation of very distinct elements which are, (1) White Anorthite, entirely soluble in hydrochloric acid; (2) Augite of a grayish-green color. This rock forms a vein in the carboniferous limestone in the district of Carlingford, Ireland. The proportion of Silica is 47.52%, and its density is 2.757. (Haughton).

48. Peperine (Syn. Tufa; Volcanic or Basaltic Tuff).-A mass of a cinder-gray or of a yellowish-brown color, sometimes reddish, or of intermixed colors; earthy, brittle, porous or cellular, recalling Wacke by its appearance, and enclosing fragments of basaltic rocks with their crystals broken or intact, Augite, black Mica, Magnetite, Amphigene, Zeolites; sometimes, also, fragments of Calc-spar or Dolomite. When the angular fragments of Basalt are dominant, the mass is called Basaltic Breccia. These breccias occur intermingled with the Basalts. In the Basaltic conglomerates, the fragments are rounded.

Tuff with Palagonite.-Tufas which enclose a more or less large quantity of granular Palagonite. Palagonite is a hydrated silicate of Alumina, Iron, Lime, Magnesia, Potash, and Soda; making a jelly in hydrochloric acid; fusible to a black magnetic bead before the blow-pipe. It is of a yellow color, often brown or black. Density 2.5; hardness, from 4 to 5. It has the appearance of amber or rosin.

Altered basalts, covered at first with an ochre-brown crust, intersected with numerous cracks owing to a chemical alteration, which reduces them, first, to a muddy gravel full of Augite crystals; and, finally, to a grayish and fertile clay.

49. Ophitone (Syn. Diabase, Mélaphyre grenu).—

Comprised under this denomination is a very important group of rocks which bear the same relation to the Melaphyres as the Dolorites to the Basalts. These, like the Dolorites, have a gran

ular texture, and are a mixture of Labradorite and Augite, ordinarily accompanied by Magnetite. They differ, mineralogically, by their accidental mixture. The Labradorite forms tabular, striated crystals, with a decided cleavage, of a grayish-white or green color. The Augite is in rather short prisms, often with very distinct cleavages. In the rock called Porphyry of Ternuay have been discovered bottle-green crystals of Pyroxene and hydrated Feldspar, with a greasy lustre, to which M. Delesse has given the name of Vosgite; the mean density of this rock is about 2.84.

Accessory elements: Magnetite, Ferruginous Chlorite.

Accidental minerals: Pyrites, Cat's eye, Epidote, Asbestos. The proportion of Augite is generally less than in the Mclaphyres. Silica varies from 45 to 53%. The density is about 2.8; it however reaches 2.93 in a number of fine-grained varieties which form part of the rocks of Sweden and Ireland, confounded with many others under the name of Trap.

Varieties: O. with medium sized grains; O. with fine grains; O. Schistose, of a gray, green, or blackish color, often colored green by chlorite, becoming yellow in hydrochloric acid; O. Calcareous, containing a great many crystals of Calc-spar, soft enough to be scratched by a steel point, very easily fusible; O. Amygdaloidal, with cavities filled with Calc-spar.

Often the Ophitones have a shagreen surface, the cavities of which are caused by the disappearance of the Feldspar. The complete decomposition of the Labradorite causes the disintegration of the rock and the production of a marl mixed with black grains of Augite.

50. Melaphyres (Syn. Ophite, Cordier; Porphyres noirs; Porphyre vert antique; Toadstone; Porphyre diabasique ou augitique; partie des Trapps et des Grünstein).-Rocks of which the color is often black, but still more often green. They are composed: (1) Of a fine-grained paste, compact, tenacious, generally black in color when the fracture is fresh, but changing to brown or reddish by alteration; often magnetic. (2) Crystals of

Augite and Labradorite of a greenish-white color, having a poorly defined contour. Generally the rock has combined with it, calc-spar, some magnetite, and chlorite, which latter colors it green.

In hydrochloric acid it effervesces and becomes yellow. Before the blow-pipe, it loses its water and becomes very clear; it fuses more or less easily into a globule of a bottle-green color. The density varies from 2.7 to 3.

Accidental minerals: Pyrites; Quartz and its varieties, Amethyst; Cat's eye; Chalcedony, distributed not in a homogeneous manner, but here and there throughout the whole in small crystalline masses; Epidote; Axinite; Green earth; Hornblende; Mica.

Varieties of composition :

(1) Melaphyres in which the proportion of Silica is inferior to that of Labradorite (53%). A number of the Melaphyres of Norway (48.76%). Melaphyres of the valley of Fassa, Tyrol, (45.65%; density 2.71 according to Streng).

(2) Silicious Melaphyres, in which the proportion of Silica is greater then 53%. Certain Melaphyres from the environs of Christiania (58.5%, after Kjerulf). Melaphyres from the left flank of Mühlenthal (57%). Amygdaloidal Melaphyres of Faucogney (54.42%; density, 2.906, according to M. Delesse). Black Melaphyres from Elbingerode, Hartz (57 to 58%).

Several eminent lithologists have thought that in the second group, the paste is a base of Oligoclase. But a certain number of Melaphyres, analyzed under the microscope by Zirkel, have shown in their mass, a more or less large quantity of vitreous matter, accompanied or not by needles of what is called Trichites; hence, probably, the great proportion of Silica.

M. Durocher remarked a long time since, that the paste of porphyries is not, in general, richer in silica than their Feldspars; and M. Delesse regards it as a magma which has not been able to crystallize.