Moisture
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STORIES FROM PHYSICS
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Fables For Children, Stories For Children, Natural Science Stori
I.
Why does a spider sometimes make a close cobweb, and sit in the very
middle of its nest, and at other times leave its nest and start a new
spider-web?
The spider makes its cobweb according to the weather, both the present
and the future weather. Looking at a spider, you can tell what kind of
weather it is going to be: if it sits tightly in the middle of the
cobweb and does no
come out, it means that it is going to rain. If it
leaves the nest and makes new cobwebs, it is going to clear off.
How can the spider know in advance what weather it is going to be?
The spider's senses are so fine that as soon as the moisture begins to
gather in the air,--though we do not yet feel it, and for us the weather
is clear,--for the spider it is already raining.
Just as a naked man will feel the moisture, when a man in his clothes
does not, so it is already raining for a spider, while for us it is only
getting ready to rain.
II.
Why do the doors swell in the winter and close badly, while in the
summer they shrink and close well?
Because in the fall and winter the wood is saturated with water, like a
sponge, and spreads out, while in the summer the water comes out as a
vapour, and the wood shrinks.
Why does soft wood, like aspen, swell more, and oak less?
Because in the hard wood, in the oak, the empty places are smaller, and
the water cannot gather there, while in the soft wood in the aspen,
there are larger empty places, and the water can gather there. In rotten
wood these empty places are still larger, and so rotten wood swells most
and shrinks most.
Beehives are made out of the softest and rottenest wood; the very best
are made from rotten willow wood. Why? Because the air passes through
the rotten wood, and in such a hive the bees feel better.
Why do boards warp?
Because they dry unevenly. If you place a damp board with one side
toward the stove, the water will leave it, and the board will contract
on that side and will pull the other side along; but the damp side
cannot contract, because it is full of water, and so the whole board
will be bent.
To keep the floors from warping, the dry boards are cut into small
pieces, and these pieces are boiled in water. When all the water is
boiled out of them, they are glued together, and then they never warp
(parquetry).