fire and smoke............................ pigeon ............................letter
We can send messages by fire and smoke.
When soldiers on a watch tower see enemies, they can send up smoke and fire. When people see the fire and smoke, they know they are in danger.
Other people can use pigeons to send and receive messages.
Sailors on a ship can use flags to signal other ships.
We can also use letters and stamps. But now we can also use telephones, Internet, and e-mails. Electricity helps us to send messages all over the world quickly and safely.