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DOMESTIC SCIENCE.

ILLUSTRANS COMMODA VITÆ

Mollo of the Royal Institution.

FIRES.

Why are coke and charcoal fires free from smoke ?

Because the moisture has been previously dissipated; this moisture producing the smoke of coal fires.

Why does too much coal on a fire cause the chimney to smoke ?

Because, when the heat begins to operate on the coal, gas is extricated; this gas carrying some of the grosser particles along with it, a heavy smoke is thrown out, which will not rise in the chimney, but by its own gravity is forced back into the room ; on which the warm air of the apartment being lighter than what comes in, instantly ascends towards the ceiling, and the lower part becomes cool. But if a portion of the fuel is taken off, then the small quantity of active caloric, or heat, acts with greater force on the unconsumed coal, brings out its latent or inactive heat more rapidly, and thereby producing a quicker decomposition of the gases, by the increasing combustion, the smoke becomes thinner and lighter, and though it carries up certainly more caloric with it proportionally than before, yet the quantity of radiant heat is greater, and the temperature of the apartment is more equalized.

Why do some chimneys smoke ?

Because the wind is too much let in at the mouth of the shaft, or the smoke is stifled below; or there is too little room in the vent, particularly where several open into the same funnel. The situation of the house may likewise affect them, especially if backed by higher buildings.

Why is a common coal fire often extinguished long before the fuel is all expended ?

Because the fire or flame left to itself is so small that it does not produce heat enough to maintain the inflaming temperature of the substance; and the remnants are not gathered together to reduce the surface of wasteful radiation. Arnott.

Why does water thrown on a brisk and flaming fire apparently increase the combustion ?

Because the water is converted into steam, which expa: ding and mixing with the flame, causes it to spread out into a much larger volume than it otherwise would have occupied. Arnott.

Why does sunshine extinguish a fire ? Because the rays engage the oxygen which had hitherto supported the fire.

Why does a fire burn briskly and clearly in cold weather?

Because the air being more dense, affords more nourishment to the fire.

Why is it wasteful to wet small coal ? Because the moisture, in being evaporated, carries off with it, as latent, and therefore useless, a considerable proportion of what the combustion produc

It is a very common prejudice, that the wetting of coal, by making it last longer, effects a great saving ; but, in truth, it restrains the combustion, and for a time makes a bad fire ; it also wastes the heat.

Why does a poker laid across a dull fire revive it?

es.

Because the poker receives and concentrates the heat, and causes a draught through the fire.

Why do vegetable stalks, &c, burn briskly?

Because of the quantity of carbon which they contain.

Why does flour of sulphur thrown into a fire-place ertinguish a chimney when on fire ?

Because, by its combustion, it effects the decomposition of the atmospheric air, which is, consequently, annihilated.

Why do certain furnaces consume their own smoke ?

Because the smoke or flame of fresh fuel, on its way to the chimney, passes through, over, or among, fuel, which, having already been converted into coko or charcoal, bad ceased to smoke; by which expedient the grosser parts of the flame or smoke are consumed, or converted into pure flame,free from smoke.

Why do we prevent a nuisance and effect a great saving by destroying or burning smoke?

Because coal containing much hydrogen, as all flaming coal does, is used wastefully when any of the hydrogen escapes without burning : for, first, the great heat which the combustion of such hydrogen would produce is not obtained ; and, secondly, the hydrogen, while becoming gas, absorbs still more heat into the latent state than an equal weight of water would, Now the smoke of a fire is the hydrogen of the coal rising in combination with a portion of carbon. Arnott.

Why are strong flames often seen at the chimney-top of foundry furnaces ?

Because the heat of the furnace is so great that the smoke burns on reaching the oxygen of the atmosphere.

Why is it evident that coal is derived from vegetation ?

Because there are few coals but that present more or less of a woody texture: to be traced from the bitumenized wood, which still bears, though approaching in its nature to coal, the trunk, the branch

1*

PART I

es, and even the very leaves of trees, through all the varieties of coal, into the most compact slaty kind, of the oldest formation. — Bakewell.

Why is charcoal sometimes found among coal ?

Because the slate which covers the coal layers takes fire, in consequence of its containing sulphur, in such minute division, as readily to attract oxygen and inflame; thus converting vegetable remains into charcoal.*

Why are charcoal and coke obtained in closed vessels ?

Because the wood and coal from which they are obtained, if similarly heated in the air, would burn or combine with the oxygen of the air; but heated in a vessel or place which excludes air, they merely give out their more volatile parts.

Why do fatal accidents happen from the burning of charcoal in chambers ?

Because of the abundance of carbonic acid gas extricated during the combustion.

Why are the insides of water casks charred, or slightly burned?

Because the charcoal thus produced in the casks, keeps the water sweet, and, in some measure, preserves the wood from the influence of damp.

Why are long, shallow stove-grates, uneconomical ?

Because the body of the coal is not soon heated, and requires to be oftener replenished, to keep up the fire.

Why is the extreme heat of sloves for heating rooms, pernicious to health ?

Because, if the temperature be thus raised much higher than 300° Fahrenheit, the animal and vegetable matter, which is found mechanically mixed at all times with the air, will be decomposed, and cer

* This curious fact is recorded by Dr Richardson, the naturalist, in Franklin's Expedition of Discovery, respecting the shale on the coasts of the Arctic Sea. This shale composed precipitous banks, which, in many places, were on fire.

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