pig-lead. A small quantity of silver generally found in the ore- from one to thirty ounces in a ton of lead. Rolled into sheets on tables. Leadworks very unhealthy; workmen suffer from colic, palsy, debility, &c.; cattle feeding in the neighbourhood are also affected.

England exports lead to France, Holland, Russia, India, Brazil, British America. Annual value, one hundred and eighty thousand pounds.

IV. Uses.

Draw from the children the uses to which it is applied, e. g. :

1. Roofing for houses, churches, &c.

2. Cisterns, pipes, rain-gutters, &c.

3. Bullets and shot: molten lead mixed with

arsenic, poured through a colander from a lofty tower or into a pit; forms globules, received into a vessel filled with water; dried on heated plates; sorted and packed. Bullets made in moulds.

4. Rusted and formed into pigments - red and white lead.

5. Enters into the manufacture of glass-pasteimitation of diamonds and other precious stones. 6. Black lead-pencils-placed in grooved cases of cedar.

7. Alloys type-metal-four parts of lead, one of antimony; pewter one fifth lead, four fifths tin; solder. equal parts of tin and lead.

LESSON V. MERCURY.

I. Appearance, Qualities, &c.

INTRODUCE the lesson by placing a small portion of quicksilver before the children, and elicit the

particulars by questions. A fluid; only metal found in that state; resembles water, oil, or melted silver hence name, quicksilver. Becomes solid when exposed to intense cold (seventy-two degrees below zero); where would this occur?-is then malleable and ductile. One of the heaviest of metals-thirteen and a half times heavier than water. Boils at six hundred and sixty degrees three times as great heat as required to boil water. Sometimes found pure, generally with ores, especially with sulphur (i. e. as cinnabar). Expanded by heat; compressed by cold.

II. Localities whence procured.

Found in many parts of the world; in small quantities. In Europe-Spain, Austria, borders of the Rhine, France, Sweden. In Asia Japan, China, Ceylon. In America-Mexico. Principal European mines :

1. Almaden in Spain, in Sierra Morena, sixteen miles north of Cordova.

2. Idria in Hungary, about twenty-five miles north-east of Trieste; eight hundred feet deep. Discovered by a peasant, soaking a new pail in a stream; filled it with sand; found it very heavy; carried some of its contents to the village priest; when examined, mercury found mixed with the sand. Afterwards mines were worked. They took fire in 1803; attempts made to smother the fire; the adjoining houses and buildings shattered as by an earthquake; ultimately subdued by introduction of water; works destroyed; three years before work re-commenced.

3. Deuxponts in Germany.

American mines discovered by the cinnabar used

by the Indians in painting their bodies; destroyed -the pillars being removed, the roof fell in.

III. Method of Preparation, &c.

When pure, collected in iron jars; obtained from cinnabar; ore broken; carefully picked; reduced to powder; mixed with lime in an iron retort (describe this vessel); strong heat applied; sulphur and lime combine; the quicksilver set free. A hundred-weight of ore produces about ten ounces of mercury. The produce of the Spanish mines conveyed on mules to Seville, in bags of sheepskins (each containing about fifty pounds), enclosed in two other similar coverings, and placed in barrels; why? The fumes very injurious; miners afflicted with various diseases palsy, blindness, fetid breath, paralysis, &c.; the deleterious vapours raised by heat; mines worked, therefore, chiefly in the winter season.

IV. Uses.

Used principally:

1. In refining gold and silver by amalgamation. Imported into China, India, Peru, Mexico, and Chili; why?-exported from Spain.

2. In gilding: mercury and gold mixed applied to copper articles (e. g. gilt buttons); the former driven off by heat.

3. In silvering looking-glasses: tinfoil and mercury placed upon the plate; pressure applied for several days; the two adhere to the glass.

4. Vermilion for paint and colouring sealing-wax prepared from it.

5. In the manufacture of barometers and thermometers.

6. In medicine (e.g. calomel), a poison.

LESSON VI.-SALT.

EXAMINE a small quantity and elicit :

I. Appearance and Qualities.

Color, white; sparkling; granulous or crystallised; hard; soluble; sapid; kinds-bay, common. II. Whence procured.

1. The sea an immense storehouse of it; the chief source. Notice its extent; covers an expanse of one hundred and forty millions of square miles, and contains from two and a half to three per cent. of salt; saltness greater towards the tropics, less near the poles; whence this difference? From what does the saltness proceed? It has been supposed from vast beds of salt at the bottom, or from saline particles brought down by the rivers. Most probably a property given by GOD at the

creation.

2. From the water of salt-springs, e. g., those of Droitwich in Worcestershire.

3. From mines, rock salt, e. g., Northwich and Nantwich in the valley of the Weaver in Cheshire; France, Hungary (Carpathian Mountains), Poland, Spain, Persia, Siberia. A salt hill in Catalonia, four hundred feet in height and three miles in circumference. In India, a whole range of salt hills. Salt plains in the Sahara and Abyssinia; latter contains one of four days' journey in extent. Most remarkable mines: - That of Wielitckza; of great depth; a mile long; half a mile broad; contains houses, stables, streets, a church, statues, &c., cut out of solid salt. Those of Salzbourg; worked by admitting water, which, when saturated with salt, is pumped out, and the water evaporated by artificial heat.

III. Process of Preparation.

Water of the sea conducted into shallow "pans" or pits, lined with clay; why? Heat of the sun evaporates the water; salt left in crystals; operation repeated till a thick layer of salt is produced; removed for purification. Salt water of springs placed in pans over furnaces; water evaporated by artificial heat; solid masses of salt left; bullocks' blood stirred in brings away impurities. Rocksalt; the impure dissolved in water; consolidated again by heat. Bay-salt is largely procured from sea water by the Spaniards and Portuguese, especially at Setubal.

IV. Uses.

a. Used in food for men and cattle; highly beneficial to health; assists in the assimilation of our food(best for culinary purposes, that obtained from the sea). Twenty pounds consumed by each person in England annually; in France, fifteen pounds. Cattle in Canada return at frequent intervals to the farms for it; when supplied, retire to the woods and pasture-grounds again. The fine wool of the Spanish sheep attributed to the quantity of salt they eat.

b. Preserves the ocean from putrefaction and corruption.

c. Increases its density; large bodies enabled to float upon its surface; e.g., vessels traversing the Black Sea carry smaller cargoes than when passing through the Mediterranean; why? the former is sixteen times less salt than the latter.

d. Preserves food, especially for long voyages. e. In medicine e. g., Epsom salt or sulphate of magnesia. "There are some saline springs in which sulphate of magnesia is a leading ingredient,