What did people do to communicate in ancient times? Here are some very interesting answers to this question.
Alphorns （阿尔卑斯长号角）were once used to communicate in the mountains in Switzerland. They are very long and they are very heavy, too. So, alphorns are hard work to blow. Then why use them? Well, they make a loud sound which travels much further than the human voice. Herdsmen （牧民）used them to call cows in the distance for milking. At sunset, alphorns were also used to send a message down to villagers that all was well. These days, they're mostly used as musical instruments.
The people of La Gomera, an island in Europe, have their own special way of sending messages from mountain to mountain. They use a whistled （口哨的）language called el silbo which comes from their language Spanish. Whistling can be heard within five kilometers, which means it can be used across much greater distances than shouting. El silbo can be used for all kinds of messages, including greetings and announcements. El silbo is used a lot less than it used to be, but primary school students in La Gomera have to learn it.
Did you know it's also possible to send messages without making a noise? This is called visual communication, and it includes the use of flags and even smoke. Long ago, soldiers along the Great Wall of China used smoke as a warning. If they noticed the enemy from their signal（信号） tower, they lit a smoky fire. When soldiers in other towers saw the smoke signal, they lit fires too. In this way, messages about the enemy's arrival could travel as far as 800 km in just a few hours.
