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1. Alumine, argil, or pure clay, is infusible by the greatest heat; but beat wakes it so hard as to scratch glass. It readily absorbs water, and also grease; and hence its use, as fuller's earth, in scouring cloths, &c.

2. Lime, or calcareous earth, is obtained by applying heat to chalk, marble, lime-stone, &c. by which carbonic acid gas and water are expelled, and the lime left as a product.

When used as a cement in building, water is used to make it plastic; and, with the addition of ashes, or sand, to supply carbonic acid, acquires its original hardness.

Lime is also used in tanning: in making sugar and soap and it forms 80 parts, combined with 20 of phos phoric acid, in 100 parts of animal bones.

Lime is antiseptic; a few drachms, stirred in a cask of impure water, will render the whole perfectly sweet. 3. Magnesia, is a soft, white earth, generally found in combination with sulphur. United with sulphuric acid, it forms that sulphate called Epsom-salts.

4. Silex, or flint, is the principal ingredient of stones, crystals, sand, &c., and cannot be melted by itself in any heat; but in contact with alkalies, as soda or pot-ash, it forms that useful production called glass.

522. The immense stony, masses of which the globe is composed, are found in the earth lying in strata one above another; a rock of one kind covering another species of rock; this a third, and so on. The arrangement is not arbitrary; but cach species occupies its regular place, from the deepest part yet explored, to the surface.

Obs.-Rocks are divided into five classes or formationst called primitive, transition, stratified, alluvial, and volcanic

1. The primitive formations of rocks are the lowest; and are supposed to have been chemical precipitations, formed in the chaotic state of the earth; because they have no petrifactions or trace of organized beings. They are chiefly composed of silicious and argillaceous earths, as granite, slate, &c.

2. Transition-rocks are supposed to have been formed during the transition of the earth into a habitable states

and differ from primitive, in the variety of their colouri, and in containing the remains of marine animals.

3. Stratified rocks are disposed in horizontal stratuz they contain the remains of animals and vegetables, aud consequently were formed after the creation of animals, and vegetables.

4. Alluvial formations consist of the constituent parts of previous rocks, separated by water, air, &c. and deposited in beds. These are compounded of sånd, gravel, loam, clay, turf, &c.; and contain plants, roofs, moss, bones, &c.; likewise petrified wood, and skeletons of quadrupeds-the remains of destroyed worlds.

5. Volcanic formations are minerals thrown out of the crater of a volcano, consisting of pumice-stones, fava, and basalts.s

523. All Acids consist of certain bases combined with oxygen, which is considered as the general cause of acidity.

Obs. 1.-Acids excite a sour taste on the tongue; change vegetable blue colours into red; and are either solid, liquid, or gaseous, Acids unite with water in every proportion, and some of them have such an affinity for it, as never to quit their fluid state. They also combine with the alka lies, earths, and metallic oxydes forming salts.

2.-Salts may be formed by art; but many exist in mature, ready formed. Salts possess double names; for example, the Nitric Acid combined with Potass forms what is called Nitrate of Potass.

524. There is also another property in nature, called the alkaline, which is distinguished from the acid by its burning and urinous taste; and it has the distinct property of converting vegetable blues into greens.

The two alkalies are potass and soda; and there is also a volatile alkali called ammonia. Obs. 1.--Alkalies and acids have the property, when combined, of neutralizing each other; and hence acids, when combined with alkalios, form what are called Neutral Salts.

: 2-Alkalies, mixed with fats, make soap; and, when melted, with silex, glass.

S. Potass is chiefly obtained by burning vegetables, as kali, &c., and hence called pet-ashes; but So the other alkali, is obtained from sea-salt, from natroa beds, and even from mines. Ammonia is obtained froça aoi. mal substances, viz. bones and urine; and also in the distillation of coals for gas.

525. The several Acids hitherto discovered are 44 in number.

11 Mineral, 8 dictalsic. 13 Vegetable Acids. 12 dainal delan

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526. The principal Acids obtained by the mixture of oxygen with other substances, are Oxygen and sulphur, called sulphuric acid, or vil of vitriol.

Oxygen and nitrogen, called nitric acid, which dissolves silver, and thence the art of plating with silver.

Oxygen and Chlorine called muriatic acid, or acid of sea salt;-this acid, united to soda, is called muriat of soda, which is the common sait of the table.

Obs. 1.-Oxygen, and Fluorine, obtained from Deeba shire-spar, is called fluoric acid, and is employed t etching on glass. Nitro-muriatic acid, or aqua engli dissolves gold and platina.

2. "Acids may combine with two or more substances, and the product is called a triple compound. Thas sulphuric seid, combined with alumine and potass, forms alum, or sulphat of alumine and potass; and Tartar emetic is the tartrate of the metal antimony, and potass,

527. SALTS formed from acids combined with alkalies, earths, or oxydes, amount to many thousands.

Those of which sulphuric acid, or oil of vitriol, forms a part, are-

Sulphate of Soda,"

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Sulphate of Magnesia,
Alumine,

- Tron,

Copper, &c.

Those of which Nitric Acid are formed, are

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Nitric and Muriatic Acid combined, form Nitro-Muriates. These are

Nitro-Muriate of Gold,

Tin,

Nitro-muriate of Cobalt,

528. Metals are seldom found in the earth in a pure state, but generally in combination with oxygen, earths, sulphur, and acids, In these states of combination, they are called ores; and are generally found in mines. (See arti ele Metallurgy, p. 16.)

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“༔ tĪ་-། ༈ Obs. 1.-Metals are fusible by heat, and when suffered to cool gradually, they crystallize.' If they are ech

tinued in fusion, they absorb a certain portion of oxygen, Juse their brilliancy, and become metallic oxydes, Water also oxidates metals; its hydrogen being disengaged, the oxygen unites with the metal Metals are soluble in acids, and may be precipitated from then by alkalies. When perfectly fused, they are miscible with each other, forming alloys, and with other substances, as sulphur, phosphorus, and charcoal,

2.In the reduction of metals from their oxydee, the addition of a combustible substance is necessary; ehacoal for instance, Iron und platina grow soft before they fuse, hence their useful property of being welded. Metals are excellent conductors of electricity. All me tals are combustible, and come will burn before they are hot enough to melt.

3.The property which metals possess of being combined with each other, renders them very useful. Copper and zinc form brass; lead and tin, pewter 329. The Metals at present known, are 28 în number.

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530. All Mineral Waters are formed by the solution, or mixture in them, of oxygen or nitrogen gases, or of acids, alkalies, and neutral salte.

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