1800s they came up with the combination
that is still used today.
To make cement, large blocks of a type
of stone called limestone are crushed or
ground into small stones. The stones
are then mixed with other minerals and
ground some more. The result is then
sent to an oven that is shaped like a
giant tube. The materials are heated to
a very high temperature as they flow
down the tube. Some of the materials
A beautiful gold bowl displays the skill of
Celtic artists.
A construction worker pours concrete.
Cement is one of the main ingredients of
concrete.
68 Cement BRITANNICA STUDENT ENCYCLOPEDIA
melt. This liquid mixes with the solid
materials to form cement chunks about
the size of marbles. The chunks are
called clinker.
After the clinker leaves the oven it is
allowed to cool. It is then mixed with
another mineral called gypsum and
ground to a fine powder. That powder is
the finished cement.
#More to explore
Concrete
Censorship
Sometimes governments or other powerful
groups set limits on people’s freedom
to speak or publish. This is called censorship.
People who practice censorship
are called censors.
Censors may examine books, newspapers,
magazines, and speeches. They
may also review paintings, photographs,
films, television shows, songs, e-mails, or
other materials. If censors find information
they do not want people to see or
hear, they may ban the material, or keep
it from being passed around. They may
cut the information out of the material.
Sometimes they may even punish the
person who created the material.
Types of Censorship
Many types of censorship exist. People
fight to ban books they do not like
from school libraries. School boards try
to get teachers not to teach certain
subjects in the classroom. Sometimes
advertisers do not like the television
shows on the channels where their
advertisements appear. They may refuse
to advertise on those channels if the
shows are not changed. Filmmakers
sometimes change the language or the
action in a movie to make it suitable
for a wider audience.
People agree that some forms of censorship
are necessary. A person is not free to
shout “Fire!” in a crowded theater when
there is no fire. Such an action would
cause a panic and endanger lives. Also,
governments can refuse to tell the public
certain information if the safety of the
nation is at stake. For this reason, many
countries accept a greater level of censorship
during wartime.
History
Governments and religious leaders have
practiced censorship since ancient times.
In ancient Rome, someone who criticized
the government might be fined,
removed from society, or put to death.
Until 1966 the
Roman Catholic
church kept
a list of books
that Roman
Catholics were
not supposed
to read.
A poster in New York City calls
for an end to censorship in the
arts.
BRITANNICA STUDENT ENCYCLOPEDIA Censorship 69
The early Roman Catholic church censored
anything that went against the
church’s teachings. The Inquisition, a
court of the church, could punish
people who spoke against the church.
Until modern times, printers in many
countries had to let government censors
read any work before it was published. If
the censor disapproved, the work was
not printed.
During the 1700s, people began to protest
more strongly against censorship. In
1791 the U.S. Bill of Rights limited
government censorship by guaranteeing
the freedom of speech. Since then, many
democratic nations have adopted similar
laws. However, in countries with Communist
governments or dictatorships,
censorship is still strong. The people in
these countries may do and say only
what the government approves.
#More to explore
Bill of Rights • Dictatorship
• Inquisition • Printing
Census
A census is a count of the people who
live in a country. It also tells things
about those people—their backgrounds,
what they own, and how they live. Governments
and businesses use censuses to
guide important decisions. There are
also censuses that focus on topics other
than population, such as housing, farming,
or industry.
Taking a Population Census
Censuses are expensive and take a long
time. Governments in many countries,
including the United States, take a census
only once every 10 years. Other
countries take a census every five years.
Census workers use a combination of
methods to try to reach every person.
During World War II (1939–45)
the U.S. government asked citizens
to censor their own letters
and conversations. The government
did not want people to discuss
war plans that enemies
might read or overhear.
Census workers sometimes go to people’s
homes to interview them.
70 Census BRITANNICA STUDENT ENCYCLOPEDIA
They mail question forms to homes.
They also interview people face-to-face
or over the phone. Most people have to
answer only a few basic questions. But
some people are asked for more information.
The questions cover such topics
as where the person lives, how old they
are, whether or not they are married,
and how many children they have. The
questions also ask about a person’s job,
religion, ethnic background, language,
and education.
After the information has been collected,
census workers sort and study it.
