and silvery-white mica." Nevertheless, it usually also contains more or less dark-coloured mica, also pyrite or marcasite, and locally tourmaline.

Pegmatyte sometimes appears in large, wellmarked veins, but more frequently it occurs in irregular veins, patches, and lentils, dying out in every direction. The dark-coloured mica, although the other constituents may be very coarsely crystalline, usually occurs in minute scales, but not always. a. Graphic granite [Gr. grapho, I write].-A variety of Pegmatyte, in which the constituents are so arranged as to produce figures resembling written characters.

b. Blumen granite.-"The felspar assumes a form resembling flowering-stalks."-Cotta.

c. Plumose granite. The mica assumes a plumose form, like Prince of Wales's feathers. -Jukes.

The granites belonging to this type [intrusive granite] in general are not foliated; nevertheless Forbes mentions a "foliated granite " at Edisvand, Norway; of which he says: "No doubt could be entertained of its true eruptive origin." And my colleague, Mr. R. G. Symes, describes veins of a foliated granite which he observed N.E. of Castlebar, in the co. Mayo, Ireland. In south-west Mayo, associated with very slightly metamorphosed rock, are wide dykes of foliated rock, some being typical gneiss (leaves of quartz, felspar, and mica), others hornblendic gneiss, while some apparently are formed of leaves of quartz, orthoclase, and amphibole.

Not uncommon in the intrusive granite is a structure having an aspect somewhat like foliation; and yet it cannot be so classed, as the con

stituents of the rock have no tendency to occur in leaves. Perhaps it may possibly be some kind of close, irregular, rudely parallel-jointed structure, induced during the cooling of the rock, somewhat similar to the structure called by Scrope "shrinkage fissures." This structure of the intrusive granite is scarcely perceptible in a hard specimen, but in rock masses it is conspicuous.

Granites more or less due to metamorphism, having (for the most part) been altered into granite while in their present positions as regards the associated rocks (see note, page 7).

These rocks appear to have been formed from previously existing sedimentary and igneous rocks. Those due to the metamorphism of the sedimentary and of the basic-igneous rocks, are often very similar in aspect and composition, while some of the acid-igneous rocks have changed into granite somewhat similar to the Intrusive Granite (A).

B. Granite for the most part non-intrusive; Basic or Oligoclase Granite; Scandinavian Granite [in part metamorphic].-Usually a crystalline aggregate of quartz, black and white mica, orthoclase, and oligoclase. When typical, it is a quinary granite; however it is very variable in its composition, which in part seems due to its metamorphic origin. Many minerals occur locally as adjuncts; such as amphibole, titanite, ripidolite, pyrite, marcasite, &c., forming different varieties.

NOTE.-Haughton is of opinion that the normal constituents of this class of metamorphic granite in Ireland, Scotland, Norway, Sweden, and Finland, are Quartz, Orthoclase, Oligoclase, Margarodite, and Lepidomelane.

Varieties in Composition.

A. HORNBLENDIC GRANITE.-An oligoclase granite, in which amphibole is a constituent. a. Titanitic Granite; Furbogh Granite. b. Chloritic or Ripidolitic Granite. c. Talcose Granite.

d. Epidotic Granite.

With amphibole titanite sometimes occurs, and this variety has been called Furbogh Granite, from a district in the county Galway, Ireland. In places ripidolite, talc, or epidote may be present with, or in place of, the amphibole, making varieties. The last-named mineral is supposed to be due to secondary formation.

NOTE.-Hornblendic granite by some geologists has been called "Syenitic granite." This name, however, seems not only unscientific, but also inapplicable, as the rock is not an aggregate of granite and syenyte, but of granite and amphibole [hornblende], and it is to the latter mineral that the name is intended to direct attention. Chloritic granite and Talcose granite have erroneously been called "Protogene granite," also a most incorrect name, as protogene (quartz+felspar+talc) is a constituent of neither. Furthermore, in general chloritic granite can have no relation to protogene, not containing any talc.

B. GRAPHITIC GRANITE.-With graphite in addition to mica.

C. HEMATITIC OR FERRUGINOUS OLIGOCLASE GRANITE. -With micaceous iron-ore in addition to the mica.

D. PYRITOUS OLIGOCLASE GRANITE. Containing pyrite or marcasite, or even chalcopyrite, in addition to the other constituents.

Structural Varieties.

E. PORPHYRITIC OLIGOCLASE GRANITE; Galway Granite.-Having one of the felspars developed in crystals, larger and more conspicuous than those of the other constituents. Generally, it is the orthoclase that is porphyritically developed; however, sometimes it is the oligoclase. It is the typical granite of county Galway, Ireland. F. GNEISSOID GRANITE; FOLIATED GRANITE; Gneissic Granite (Cotta).-An oligoclase granite, in which there is more or less distinct foliation. Sometimes one of the felspars is porphyritically developed, when in general the mica does not curl round the large crystals of felspar, but the latter lie promiscuously about.

a. Nodular Granite.-Containing round or semiangular pieces or nodules of a dissimilar granite or of a granitic rock. The inliers often are a hornblendic granite or a rock, like minette, or like a gneissyte, but they vary considerably.

b. Lenticular Granite.-A more or less gneissoid granite, containing lenticular patches or lentils of granite or a rock, like a gneissyte or minette. The lentils sometimes occur closely together, at other times widely apart; but in all cases the foliation of the rock curls round them.

G. INTRUSIVE OLIGOCLASE GRANITE; Omey Granite. -Very similar to the non-intrusive oligoclase granite; but such minerals as amphibole, titanite, ripidolite, &c., only occur locally, as accessories. It has been called "Omey granite," from an island on the west coast of Ireland. Besides the varieties mentioned above, others

might be named, but those given seem to be the most important.

Veins of segregation occur in the oligoclase granite. Their composition appears very similar to the veins of segregation (granityte) that occur in the highly siliceous granite, being of a more or less siliceous nature. There are also irregular veins, nests, and lenticular patches, sometimes of considerable size, of a rock answering Cotta's description for the rock called Pegmatyte. The Pegmatyte found associated with the non-intrusive oligoclase granite is, at least in some instances, due to the metamorphism of irregular felspathic veins and lenticular patches that existed in the metamorphosed sedimentary and irruptive rocks prior to their being changed into granite.

Basic igneous rocks may be metamorphosed into rocks very similar to the Basic or oligoclase granite, or its varieties; and the Acid or highly siliceous igneous rocks may change into a rock like the finer varieties of the Intrusive or highly siliceous granite (A); while the basic felstones (Euryte and such rocks) may be altered into more or less hornblendic or chloritic, or even talcose granite.

H. GRANITIC FELSTONE.-A fine, more or less evengrained aggregate of quartz, felspar, and mica. In some varieties the felspar seems always to be orthoclase; the mica may be black or white, often both. Part of the mica may be replaced by amphibole or ripidolite. They weather neither like a true granite nor yet like a felstone, having a characteristic weathering of their own, partaking of the nature of both. Granitic felstones probably are metamorphosed felstones. They are often banded, the lines so