Campfires kept people warm and scared
off wild animals. Fire lit the way at night
and in caves. Fire also cooked food.
Eventually, people used fire in new ways.
They set fires to clear land for farming.
They used fire to make pottery from
clay. By about 3500 BC people were
using fire to shape metals. As the centuries
passed, people learned to use fire to
make such things as steam, rubber, and
bricks.
#More to explore
Civilization • Combustion
Firefighting
Fire is useful to humans, but it is dangerous
as well. Fires kill thousands of
people each year and destroy much
property. The people who put out fires
are called firefighters. Firefighters also
work to prevent fires and teach fire
safety.
A fire must have fuel, oxygen, and heat
in order to burn. Firefighters put out
fires by removing at least one of those
Fire is used in many factories to operate
furnaces or heat boilers. In a steel mill it is
used to melt the materials that go into making
steel.
Early humans
did not know
how to start a
fire. They had
to get fire from
trees struck by
lightning or
from volcanic
eruptions.
BRITANNICA STUDENT ENCYCLOPEDIA Firefighting 25
three ingredients. For example, they take
fuel away from a forest or brush fire by
clearing away trees and bushes in the
path of the fire. They take oxygen away
from a grease fire by smothering it with
foam from a fire extinguisher. They
reduce the heat of a burning building by
spraying water over it.
Fire departments (also called fire brigades)
date back to ancient Rome.
Today almost all large and mediumsized
cities have full-time fire departments.
Volunteers staff many small fire
departments.
Firefighters use several kinds of equipment
at a fire. Pumper trucks carry powerful
pumps and long hoses to shoot
water at the fire. Ladder trucks and
elevating platforms are equipped to rescue
people and fight fires in tall buildings.
Tanker trucks carry water to places
that have no water pipes nearby. Airplanes
and helicopters are used to drop
water or chemicals on forest fires. Many
fire departments also provide ambulance
service for fire victims.
Deaths from fires have dropped in
recent years. More buildings now use
construction materials that do not burn
easily. And more buildings now have
automatic water sprinklers. However, in
case a fire does break out, people should
know how to contact their fire department.
They also should know where
emergency exits are and how to escape a
burning building safely. Plus, every
home should have fire extinguishers.
#More to explore
Ambulance • Combustion • Fire
Firefly
In many places the insects called fireflies
are a familiar sight on summer nights.
They are noticeable because they can
produce flashes of light. Fireflies belong
to the beetle family. They are also called
lightning bugs.
There are about 1,900 species, or types,
of firefly. They live in tropical and mild
parts of the world. They generally like
warm, humid areas, but some live in dry
places.
Firefighters wear protective clothing
because their work is sometimes dangerous.
A firefly lights up.
26 Firefly BRITANNICA STUDENT ENCYCLOPEDIA
Adult fireflies range in size from 0.2 to 1
inch (5 to 25 millimeters) long. They
have a soft, flattened body that is dark
brown or black, sometimes with orange
or yellow marks. Males have wings and
are good fliers. Females either have short
wings or no wings. The females without
wings are often called glowworms.
Young fireflies, which also have no
wings, are also called glowworms.
Fireflies produce light with special
organs, or body parts, on the underside
of the body. These organs make light by
mixing chemicals with oxygen from the
air. Fireflies make a certain series of
flashes to attract a mate. When a possible
mate sees the flashes, it returns the
signal.
#More to explore
Beetle • Insect
Fish
Fish are a kind of animal that lives in
water. Fish have lived on Earth for more
than 450 million years. There are more
than 24,000 species, or kinds, of fish.
New ones are discovered every year.
Where Fish Live
Fish live in lakes, rivers, seas, and oceans
around the world. They live in all kinds
of water, from warm springs to cold
Arctic seas. Fish can even be found in
the dark pools of underground caves.
Physical Features
The many different kinds of fish have
some things in common. They are all
vertebrates, which means that they have
a backbone. They are cold-blooded,
which means that their body temperature
changes along with the temperature
of their surroundings. Fish generally
breathe through organs called gills. They
usually have pairs of fins in place of
arms and legs. Most fish are covered
with scales.
But fish also show great variety. Gobies,
the smallest fish, can be less than half an
inch (13 millimeters) long. The whale
shark, the largest fish, can be 50 feet (15
meters) long and weigh 20 tons. A typical
fish is wider in the middle than at
the ends. But a flounder is as flat as a
dinner plate. A sea horse looks something
like a horse standing on its tail.
Eels look like snakes.
Over millions of years, some fish have
developed unique features to help them
survive. These features are called adaptations.
