G NE

G N E

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It is decompofable by’a low red heat, the acidand moifture being driven oft': it is alfo decom-pofable with effervefcence by the other acids.

Phofphat of Glycine is obtained by addingphofphat of foda, to fulphat, nitrat, or muriatof glycine: a white pulverulent precipitate fallsdown, which is the fait in queftion. Whenperfedfly neutralized it is uncryftallizable, in-ioluble in water, and infipid: at a high heat itmelts into a tranfparent glafs: when the acid isin excefs it is foluble in water. It is decom-pofable by the alkaline carbonat and alkalineearths, except carbonat of magnefia, and ,by thefulphat, nitrat, and muriat of alumine.

Sulphat of Glycine is procured by adding eitherpure or carbonated glycine to fulphuric acid tillthis la ft is perfectly faturated: by fpontaneouscryftallization, fulphat of glycine is depofited inoctahedrons compofed of two oblique four-fidedpyramids joined bafe to bafe, with the edges andfolid angles truncated. The tafte of this faitis very fweet, and fomewhat aftringent: it isreadily foluble in water, and tincture of gallsadded to the folution occafions a yellowilh whiteprecipitate. The folid fait when heated dif-iolves in its water of cryftallization, and after-wards becomes pulverulent: at a red heat theacid is entirely driven off, the pure earth beingleft behind.

If a little fulphat of potafh is added to afolution of fulphated glycine, and the liquor isflowly evaporated, a quantity of fmall cryftallinegrains are depofited which are readily foluble infeven or eight times their weight of cold water.If carbonated glycine is digefted in a folution ofcommon alum, the glycine is taken up and thealumine entirely precipitated.

Nitrat of Glycine is prepared in the famemanner as the preceding fait, by fubftitutingthe nitric for the fulphuric acid. Its tafte isfweet and aflringent, it is ftrongly deliquefeent,and when evaporated affumes the conliftence ofhoney, but does not cryftallize: like the pre-ceding falts it is decompofable by a red heat theacid being evaporated. With tincture of gallsit gives a yellowifh brown precipitate.

Muriat of Glycine both in the mode of itspreparation and in its general charadters bears aclofe refemblance to the preceding, it is how-ever capable of being, cryftaliized, which is notthe cafe with nitrat of glycine.

Neither the pure earth nor any of its faltshave been applied to any ufe.

GNEISS . 1 Gneifs is eflentially an aggregateof quartz, felfpar and mica: of thefe fubftances

the latter is in the form of extremely thin plates,all of which are arranged in the fame directionand parallel to the general inclination of theftratum. In its compofition, gneifs is the fameas granite, but differs in the arrangement of itsparts, efpecially of the mica, ■ which in graniteis difperfed throughout its fubftance in everydirection; gneifs has a flaty texture and fplitsreadily in the direction of the mica, hence fromits longitudinal fradfure it would be fuppofed tocoiifift' almoft wholly of this fubftance, whilefrom its crofs fracture it feems made up ofquartz and felfpar interrupted by very narrowlines of mica.

There are three varieties of gneifs. In thefirft each ingredient forms a diftinct ftratumirregularly alternating with the others and re-prefenting on its crofs fra&ure parallel bands ofquartz, felfpar, and mica, either even or un-dulating. This variety forms the connectinglink between granite and common gneifs, theundulatingly banded, paffing immediately intothe latter, and the even banded, which maywithout impropriety be named banded granite,granite veine of Saufftire , into the former. Thefecond variety is common gneifs: in this theingredients are more mingled than in the pre-ceding, and its fracture is coarfely flaty. Whenthe component parts are ftill more intimatelymixed, the mafs belongs to the third variety orfoliated gneifs: the fradure of this is fine flatypalling into foliated, and the mica feems toprevail, if not in quantity at leaft in efficacyover the quartz and felfpar, the characters ofwhich are obfeured by thofe of the mica: whenthe mica is very predominant, the rock paflesinto micaceous fchiftus.

The quartz in gneifs is generally of a whitilhor fmoak grey colour, and it is either opake orflightly tranfparent. The felfpar in thofe fpe-cirnens that pafs into granite is moftly flelh-red,in the others it is greyilh or yellowilh white.The mica is filvery white or tombac brownverging upon black. It fometimes though rare-ly happens that the felfpar is in a ft ate of de-compofition approaching to porcelain clay,whence fome authors have mentioned induratedclay as a component part of gneifs.

Among the fubftances accidentally inclofedin gneifs may be reckoned garnet, which veryfrequently, and fchorl which very rarely occurs,alfo fragments of granite, hornblende, and oc-caiionally fteatite. Gneifs is one of the primi-tive rocks, and in its formation is confidered asimmediately pofterior to granite, as it is ufually

* Lena, Brochant.