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2 THE_ BOY ELECTRICIAN

little use to mankind save as a curiosity which possessed
the power of attracting small pieces of iron and steel and
other magnets like itself. Then some one, no one knows
who, discovered that if a magnet-stone were hung by a
thread in a suitable manner it would always tend to point
North and South; and so the “ Magnes-stone ” became
also called the “ lodestone,” or “ leading-stone.”

These simple bits of lodestone suspended by a thread
were the forerunners of the modern compass and were of
great value to the ancient navigators, for they enabled
them to steer ships in cloudy weather when the sun was
obscured and on nights when the pole-star could not be
seen.

The first real compasses were called gnomons, and con-
sisted of a steel needle which had been rubbed upon a
lodestone until it acquired its magnetic properties. Then it
was thrust through a reed 'or short piece of wood which
supported it on the surface of a vessel of water. If the
needle was left in this receptacle, naturally it would move
against the side and not point a true position. Therefore
it was given a circular movement in the water, and as soon
as it came to rest, the point on the horizon which the north
end designated was carefully noted and the ship’s course
laid accordingly.

The modern mariners’ compass is quite a different ar-
rangement. It consists of three parts, the bowl, the card,
and the needle. The bowl, which contains the card and
needle, is usually a hemispherical brass receptacle, sus-

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