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perly laminated. When pure, it is hardly fufiblewithout a flux.

In fome varieties of micaceous fchiftus a con-fiderable quantity of felfpar is contained, whenthis is the cafe its texture becomes coarfer, andit is fcarcely to be diftinguilhed from gneifs;Other varieties confift entirely of mica and gra-nular quartz, but this latter in fo great a pro-portion to the other ingredient that its flatytexture is almoft entirely obfcured.

Micaceous fchiftus frequently inclofes otherminerals, particularly garnet, felfpar, cyanite,and tourmalin.

Mountains of micaceous fchiftus are by nomeans fo Ample in their ftrudture as thofe ofgranite and gneifs, fince they frequently containbeds of primitive limeftone, hornblende, flate,and rarely primitive gypfum ; beds of aftyno-lite, pyrites, galena, and other metallic ores arealfo occ'fionally met with. Some of the rich-eft metallic veins are alfo fituated in this fpeciesof rock, as is the cafe with mc-ft of the minesof Sweden and Norway , and with a confidera’blenumber of thofe in Saxony and Hungary . Mi-caceous fchiftus generally repofes on gneifs, andforms mountainous chains of confiderable extent,though feldom of any great heighth. The raoftinterefting chains of this fpecies of mountain inBritain are the vales of the Tay, and the Tum-mel, Strath Errick, and'Glen Roy, in the Scot-tilh highlands.

Micaceous fchiftus, when pure, is in muchrequeft for the walls and hearths of furnaceson account of its great infufibility; it is alfofpiht into leaves for covering houfes, thoughfor tihis purpofe it is inferior to flate.

MIcFArELLE. See Pinct.

MICiROCQSMIC SALT is the compoundPhosphAT of Soda and Ammonia (which fee).MILK. Milch. Germ. Lait . Fr.

This fluted, the next in importance of all theanimal liquoi 's to blood, has been examined verylargely by different chemifts, and its analyfts iscurious and important. Scheele, “ Fourcroy, band Vauquelin , L'armentier and Deyeux, 0 andmany others have given particular attention tothis fubjedl, and fr om their united labours thefollowing general account of its properties mayBe given.

Milk is a white opake fluid, varying in huefrom a yellowifh to a blueifh tint, of a foft fome-what unfluous-feel, and a fweetilh and gratefultafte. It frequently is altered in tafte and fmell•and fometimes too in colour, by the nature ofthe aliment which the animal takes. The fpe-

* I'.fT.'.yj. b 'Eacyc. Metli. A)

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cific gravity of milk varies according to theanimal that produces it, the food, and othercircumftances. The gravity of cows milk isabout 1.0203 according to Briflon,'and this isthe lighted: next to human milk. Sheeps milk,which is heavy, weighs 1.0409.

The chemical compofition of this fluid is thefame in all animals, as far as has been examined,that is, all milks confift of the fame fubftancesin intimate combination, but the relative pro-portion of thefe fubftances is probably not thelame in any two animals, and is fo remarkablydifferent in fome, as to be obvious to commonobfervers. In a general view milk may be faidto be compofed of the following ingredients.

1. Of the cafeous or curdy matter, which isfeparable from milk by various means, and par-ticularly by rennet , and which when collectedand condenfed by preflure forms cheele.

2. Of a true animal oil, butter, which isfeparable from the cream chiefly by agitation.

3. Of a fweet watery fluid, the ferum orwhey, which generally contains a good deal ofthe two former ingredients diifolved, and alfoholds a quantity of faccharine matter, of animaljelly, of muriat of foda, and potafh, and fomephofphats.

The further analyfis of thefe three fubftanceswill be prefently mentioned.

Milk when moderately heated fwells andfroths confiderably, and at about 200 0 of heatit boils. At the fame time there forms on thefurface a tough dry pellicle, which when re-moved is fucceeded by another, and fo on iuc-ceffively. This Ikin is the fame as the curd orcafeous matter obtained by the common means,and if the procefs is continued for a great lengthof time, all the curd may be feparated in thisform, and a watery liquid alone will remain.

If milk is evaporated to drynefs there remainsa folid yellowifh extra<T, known abroad by thename franchipane, and formerly ufed in medi-cine. If the vapour diftilled from boiling milkbe condenfed in a proper receiver, it forms aclear liquor of a faintifli tafte, which after long{landing becomes muddy and putrefies.

The coagulation of milk is one of the moftimportant changes which it undergoes, and iseffedled by a variety of methods. All the acidscoagulate milk, alcohol and all vinous liquorsdo the fame, and alfo feveral vegetables. Butthe fpeedieft and moft perfeft coagulation iseffected by remiet, or an infufion of the fto-mach of calves, pickled and falted, which is thefubftance ufed in making cheefe. The gaftric. Lait . e Journ. de Phyfique.

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