A Guide To The Scientific Knowledge Of Things Familiar - novelonlinefull.com
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Q. _Why are CINDERS lighter than COALS?_
A. Because their vapour, gases, and volatile parts, have been driven off by _previous combustion_.
Q. _Why will not STONES do for fuel, as well as COALS?_
A. Because they contain no _hydrogen_ (or inflammable gas) like coals.
Q. _Why will not WET KINDLING light a fire?_
A. 1st--Because the moisture of the wet kindling prevents the _oxygen of the air from getting to the fuel_ to form it into carbonic acid gas: and
2ndly--The heat of the fire is perpetually _drawn off_, by the conversion of _water_ into _steam_.
Q. _Why does DRY wood burn BETTER than GREEN?_
A. 1st--Because no heat is _carried away_, by the conversion of _water into steam_: and
2ndly--The pores of dry wood _are filled with air_, which supply the fire with oxygen.
Q. _Why do TWO pieces of WOOD burn BETTER than ONE?_
A. 1st--Because they help to entangle the _heat of the pa.s.sing smoke_, and _throw it on the fuel_: and
2ndly--They help to _entangle the air_ that pa.s.ses over the fire, and create a kind of _eddy_ or draught.
Q. _Why does SALT CRACKLE when thrown into a FIRE?_
A. Salt contains _water_; and the _cracking_ of the salt is owing to the sudden _conversion of the water into steam_.
Q. _Why will not wood or paper burn, if they are steeped in a solution of POTASH, phosphate of LIME, or AMMONIA (hartshorn)?_
A. Because any "al'kali" (such as potash) will _arrest the hydrogen_ (as it escapes from the fuel), and prevent its _combination_ with the _oxygen of air_.
Q. _What is an al'kali?_
A. The con'verse of an _acid_; as _bitter_ is the con'verse of _sweet_, or _insipid_ the con'verse of _pungent_.
Q. _Why does a JET of FLAME sometimes burst into the room THROUGH THE BARS OF A STOVE?_
A. The iron bars conduct heat to the _interior of some lump of coal:_ and its volatile gas (bursting through the weakest part) is kindled by the glowing coals over which it pa.s.ses.
Q. _Why is this JET sometimes of a GREENISH YELLOW colour?_
A. When a lump of coals lies _over the hot bars_, or the coals below it are not _red hot_, the gas which bursts from the lump _escapes unburnt_, and is of a greenish colour.
Q. _Why does the gas escape UNBURNT?_
A. Because neither the _bars_ nor _coals_ (over which it pa.s.ses) are _red-hot_.
Q. _Why does a BLUISH FLAME sometimes flicker on the surface of hot cinders?_
A. Gas from the hot coals _at the bottom of the grate_ mixing with the _carbon of the coals above_, produces an inflammable gas (called carbonic oxide), which burns with a blue flame.
Q. _Why is the FLAME of a good fire YELLOW?_
A. Because both the hydrogen and carbon of the fuel are in a state of _perfect combustion_. It is the _white heat of the carbon_, which gives the pale yellow tinge to the flaming hydrogen.
Q. _What is LIGHT?_
A. Rapid _undulations_ of a fluid called _ether_, striking on the eye.
Q. _How does COMBUSTION make these undulations of LIGHT?_
A. The atoms of matter (set in motion by heat) _striking against_ this ether, produce _undulations_ in it; as a _stone_ thrown into a stream, would produce undulations in the _water_.
Q. _How can UNDULATIONS of ether produce LIGHT?_
A. As _sound_ is produced by _undulations of air_ striking on the _ear_; so _light_ is produced by undulations of _ether_ striking on the _eye_.
Q. _What is ETHER?_
A. A very subtile fluid, which pervades and surrounds _every thing we see_.
Q. _Mention a simple experiment to prove that LIGHT is produced by rapid MOTION._
A. When a fiddle-string is _jerked_ suddenly, its rapid vibration produces a grey _light_; and when a carriage wheel revolves very quickly, it sends forth a similar light.
Q. _Does HEAT ALWAYS produce LIGHT?_
A. No: the heat of a stack of hay, or reeking dunghill, though very _great_, is not sufficient to produce _light_.
