A Guide To The Scientific Knowledge Of Things Familiar Part 5

Q. _Why is it better to be WET than dry?_

A. Because the _wet clothes_ would form a far _better conductor_ than the _fluids of our body_; and, lightning would roll down the wet clothes, _without touching our body at all_.

Q. _What is the SAFEST thing a person can do to avoid injury from lightning?_

A. He should draw his bedstead into the middle of his room, commit himself to the care of G.o.d, and go to bed; remembering that our Lord has said, "The very hairs of your head are all numbered."

Q. _What is a LIGHTNING-CONDUCTOR?_

A. A metal rod fixed in the earth, running up the whole height of a building, and rising in a point above it.

Q. _What metal is the best for this purpose?_

A. Stout copper wire.

Q. _Why is COPPER wire better than iron?_

A. 1st--Because copper is a better conductor than iron:

2ndly--It is not so easily fused or melted: and

3rdly--It is not so much injured by weather.

Q. _What is the GOOD of a lightning-conductor?_

A. Metal wire is a most excellent conductor; and as the lightning makes choice of the _best conductors_, it would run down the _metal wire_, rather than the _bricks_ of the building.

Q. _How far will the beneficial influence of a lightning-conductor extend?_

A. It will protect a circ.u.mference all round, the diameter of which is (at least) 4 times as long as that part of the rod, which _rises above the building_.

Q. _Give me an example._

A. If the rod rise 2 feet above the house, it will protect the building for (at least) 8 feet all round.

Q. _Why are not lightning-conductors more generally used?_

A. Because they are often productive of more harm than good.

Q. _How can lightning-conductors be productive of HARM?_

A. If the rod be _broken_ by weather or accident, the electric fluid (being obstructed in its path) will rend the building into fragments.

Q. _Is there any OTHER evil to be apprehended from a lightning rod?_

A. Yes; if the rod be not big enough to conduct the _whole_ current to the earth, the lightning will _fuse_ the metal, and greatly injure the building.

Q. _How stout is it needful for the copper wire to be, that it may conduct the fluid safely to the earth?_

A. It should be (at least) _one inch_ in diameter.

Q. _Why does LIGHTNING sometimes KNOCK DOWN HOUSES and churches?_

A. The steeple, or chimney is first struck; the lightning then darts to the iron bars and cramps employed in the building; and (as it darts from bar to bar) shatters to atoms the bricks and stones, which oppose its progress.

Q. _Can you tell me how St. Bride's Church (London) was nearly destroyed by lightning, about 100 years ago?_

A. The lightning first struck the metal vane, and ran down the rod; it then darted to the iron cramps, employed to support the building; and (as it flew from bar to bar) smashed the stones of the church, which lay between.

Q. _Why did the lightning fly about from place to place, and not pa.s.s down in a straight course?_

A. Because it always takes in its course the _best conductors_; and will fly both right and left, in order to reach them.

Q. _Why does LIGHTNING turn MILK SOUR?_

A. Lightning causes the gases of the air (through which it pa.s.ses) to _combine_, and thus produces a poison, called _nitric acid_; some small portion of which, mixing with the milk, turns it sour.[2]

(N. B. Sometimes, the mere _heat_ of the air, during the storm, turns milk sour.)

[2] The air is composed of two gases, called oxygen and hydrogen, _mixed_ together, but _not combined_. If oxygen is _combined_ with nitrogen, it produces five deadly poisons, viz.--nitrous oxide, nitric oxide, hyponitrous acid, nitrous acid, and nitric acid, according to the proportion of each gas in the combination.

Q. _What is the difference between COMBINING and MIXING?_

A. When different ingredients mingle _without undergoing any chemical change_, they are said to be _mixed_; but when the natural properties of each are _altered by the union_, then those ingredients are said to be _combined_.

Q. _Give me an example._

A. If different coloured sands be shaken together in a bottle, the various grains will _mix_ together, but not combine: but if water be poured on quick lime, the water will _combine_ with the lime, and not mix with it.

Q. _Why are the different grains of sand said to be MIXED, when they are shaken together?_