Mountains
The Allegheny Mountains, or the
Alleghenies, extend from Pennsylvania
to Virginia in the eastern United States.
They are noted for their scenic beauty.
At one time these mountains were an
obstacle to settlers who wished to move
westward.
Muhammad Ali fights Ernie Terrell
in 1967.
82 Ali, Muhammad BRITANNICA STUDENT ENCYCLOPEDIA
The Alleghenies are part of the Appalachian
Mountains. They stretch more
than 500 miles (800 kilometers) and
consist of two nearly parallel ridges.
At Mount Davis near the Maryland border,
the Alleghenies rise to 3,213 feet
(979 meters), the highest point in Pennsylvania.
The highest point inWest Virginia
is 4,863 feet (1,482 meters), at
Spruce Knob.
A large amount of coal is mined from
the Allegheny range. Heavy forest cover
makes the Alleghenies a rich source of
timber, too.
#More to explore
Appalachian Mountains
Allen, Ethan
Ethan Allen was a patriot and a soldier.
He won an important early victory in
the American Revolution. Allen led a
band of fighters called the Green Mountain
Boys against the British at Fort
Ticonderoga, in what is now New York.
Ethan Allen was born on January 21,
1738, in Litchfield, Connecticut. In
1757 he fought in the French and
IndianWar. In 1762 Allen became an
ironworker. Several years later he moved
to what is now Vermont.
Vermont was not a separate colony at the
time. NewHampshire and New York
both claimed the territory.To aid the
NewHampshire side in the dispute,
Allen organized the GreenMountain
Boys. (The name of Vermont comes from
the French words for green mountain.)
After the start of the American
Revolution, the group fought the British.
On May 10, 1775, the Green Mountain
Boys captured Fort Ticonderoga. Later
that year Allen was captured by the British
during an unsuccessful attack on
Montreal, Canada. He was released in
1778. The Army then made him a colonel,
but he fought no more in the war.
The Allegheny Mountains become very colorful
in the fall as the leaves on the trees
begin to change.
A picture from the 1800s shows Ethan Allen
capturing Fort Ticonderoga.
BRITANNICA STUDENT ENCYCLOPEDIA Allen, Ethan 83
Allen spent his later years trying to make
Vermont a state. New York still wanted
the territory for itself and interfered with
his efforts. After the war Allen even
talked with the British about making
Vermont part of Canada. This hurt his
reputation as an American patriot. He
died on February 12, 1789, in Burlington,
Vermont.
#More to explore
American Revolution French and
IndianWar Vermont
Allergy
An allergy is the human bodys negative
reaction to certain foreign substances.
Some allergies are commonplace. Many
people suffer from hay fever when pollen
is in the air. Some develop skin
rashes when they touch certain substances.
Others experience stomach
cramps after eating particular foods.
When a person reacts in these ways to
any outside substance, that individual is
said to be allergic to it.
Allergies and the Immune
System
Several things happen to cause an allergic
reaction. First, a person is exposed to
a substance such as pollen. The bodies of
most people would simply ignore pollen.
Some peoples bodies, however, treat it
as a harmful invader. When this happens,
the persons immune system produces
substances called antibodies to
fight the pollens effects.
The antibodies produced in the body
tend to stay in the blood. Because of
this, the immune system remembers and
recognizes the specific substance that
attacked the body. The next time the
body comes in contact with the substance,
the antibodies react to it again.
Signs of an Allergic Reaction
The antibodies react by releasing a
chemical called histamine. Histamine
causes fluid to build up in the body and
cell tissues to swell. That is why the eyelids
of a person with hay fever become
red and puffy. Histamine also affects
muscles. This can cause breathing difficulties
or stomach cramping and pain.
One severe type of allergic reaction is
known as anaphylactic shock, or anaphylaxis.
Some people have this reaction
if they take certain drugs, eat foods such
as nuts and shellfish, or get stung by
certain insects. Anaphylaxis has very
severe symptoms and sometimes leads to
death.
Treatment
Most people quickly learn which allergies
they have. When possible, they try
Sneezing is a common sign of some allergies,
such as hay fever.
Pets are a
common cause
of allergies.
Skin cells and
saliva of cats,
in particular,
can cause
sneezing, itching,
and
watery eyes.
84 Allergy BRITANNICA STUDENT ENCYCLOPEDIA
to avoid contact with the substance that
causes the allergy. Unfortunately, substances
such as dust and pollen are
everywhere. Taking drugs known as antihistamines
can decrease the allergic reactions.
Antihistamines prevent histamine
from reaching the cell tissues.
#More to explore
Asthma Immune System
Alligator
Alligators are large lizardlike animals
with long, rounded snouts and powerful
tails. They spend most of their time in
the water, but they also travel on land.
Alligators belong to the group of animals
called reptiles. They are related to
crocodiles.
Where Alligators Live
Alligators live along the edges of
swamps, lakes, and slow-moving rivers.
There are two species, or types, of alligator.
The American alligator lives in the
southeastern United States. The Chinese
alligator lives in the Yangtze River region
in China. It is very rare.
Physical Features
Male American alligators measure about
11 feet (3.4 meters) in length on average.
The females are slightly smaller.
Young American alligators are black
with yellow stripes on the tail. The
adults are brownish.
The Chinese alligator normally grows to
a length of about 5 feet (1.5 meters). It is
blackish with faint yellowish markings.
Alligators have many features in common
with crocodiles. They have thick
skin composed of many scales and
plates. They each have a long body and
four short legs. The eyes, ears, and nostrils
are located on top of the head.
These show above the water when the
animal floats.
However, there are easy ways to tell alligators
and crocodiles apart. One of the
most obvious is that alligators have
broad, rounded snouts, while most
crocodiles have narrow, pointed snouts.
Behavior
Alligators eat mainly fish, small mammals,
and birds. But they sometimes kill
American alligator prey as large as deer or cattle.
A view from above shows the different
snouts of an alligator and a crocodile.
BRITANNICA STUDENT ENCYCLOPEDIA Alligator 85
Alligators usually mate during the
spring. The female builds a nest of mud
and grass. She lays 20 to 60 white eggs
in the nest. The eggs hatch after about
65 days. The young alligators live with
their mother for as long as a year.
#More to explore
Crocodile Reptile
Allosaurus
Allosaurus was a fierce dinosaur that
roamed Earth before the similar but
more well-known Tyrannosaurus rex
appeared. The name Allosaurus means
other lizard. Allosaurus is a member of