题型：阅读理解 题类：常考题 难易度：普通
广东省华附、省实、广雅、深中2019届高三上学期英语期末考试试卷
Your mobile phone vibrates in your pocket. 'Need to see you,' reads the screen. Nothing new, considering that texting is currently the most common form of long-distance communication. But how were messages conveyed in the past?
One of the first methods was the smoke signal. This practice was used by Chinese soldiers guarding the Great Wall to warn of the enemy's approach. The Greeks invented a whole alphabet of smoke signals for sending messages. But it was Native Americans who made the system mobile by carrying small bunches of dried grasses around with them. These could be lit quickly from any place at any time.
Moving on to messages transmitted by sound, an early technique was the drum. Drums are still used today in the rainforests of Africa, Papua New Guinea and Central and South America for broadcasting news. The instrument is made from a piece of wood, which is empty inside, and this is hit with a stick. On receiving the message, each village passes it on to the next, which means that news can travel at up to 150 km an hour.
In some parts of the world, humans are able to convey messages over long distances without using instruments. On La Gomera, one of the Canary Islands, people use Silbo, or the 'whistling language' to communicate across the valleys. The language involves the use of the tongue, lips and hands to make sounds, which can travel up to 5 km. To ensure its continuation, Silbo is currently a compulsory subject in primary and secondary schools on the island.
A look at long-distance communication would not be complete without mentioning the art of yodelling. This is a form of singing, in which the voice changes sound levels very quickly, making it easily heard over long distances. It is believed that the technique was developed in the Swiss Alps, but it is also found in other places such as Central Africa. At one time, yodelling was popular in theatres and music halls, but this is no longer so.
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