The smoke signal is one of the oldest forms of communication in recorded history. It is a form of visual communication

Visual communication

Visual communication as the name suggests is communication through visual aid and is described as the conveyance of ideas and information in forms that can be read or looked upon...

 used over long distance.

History and usage

In Ancient China, soldiers stationed along the Great Wall would alert each other of impending enemy attack by signaling from tower to tower. In this way, they were able to transmit a message as far away as 750 kilometres (466 mi) in just a few hours.

Polybius

Polybius

Polybius , Greek ) was a Greek historian of the Hellenistic Period noted for his work, The Histories, which covered the period of 220–146 BC in detail. The work describes in part the rise of the Roman Republic and its gradual domination over Greece...

, a Greek historian

Historian

A historian is a person who studies and writes about the past and is regarded as an authority on it. Historians are concerned with the continuous, methodical narrative and research of past events as relating to the human race; as well as the study of all history in time. If the individual is...

, came up with a more complex system of alphabetical smoke signals around 150 BC. He invented a system of converting Greek alphabetic characters into numeric characters. It was devised to enable messages to be easily signaled by holding sets of torches in pairs. This idea, known as the "Polybius square

Polybius square

In cryptography, the Polybius square, also known as the Polybius checkerboard, is a device invented by the Ancient Greek historian and scholar Polybius, described in , for fractionating plaintext characters so that they can be represented by a smaller set of symbols.-Basic form :The original square...

", also lends itself to cryptography

Cryptography

Cryptography is the practice and study of techniques for secure communication in the presence of third parties...

 and steganography

Steganography

Steganography is the art and science of writing hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message, a form of security through obscurity...

. This cryptographic concept has been used with Japanese Hiragana

Hiragana

is a Japanese syllabary, one basic component of the Japanese writing system, along with katakana, kanji, and the Latin alphabet . Hiragana and katakana are both kana systems, in which each character represents one mora...

 and the Germans in the later years of the First World War.

The North American Indians also communicated via smoke signal. Each tribe

Tribe

A tribe, viewed historically or developmentally, consists of a social group existing before the development of, or outside of, states.Many anthropologists use the term tribal society to refer to societies organized largely on the basis of kinship, especially corporate descent groups .Some theorists...

 had their own signaling system and understanding. A signaler started a fire on an elevation typically using damp grass, which would cause a column of smoke to rise. The grass would be taken off as it dried and another bundle would be placed on the fire. Reputedly the location of the smoke along the incline conveyed a meaning. If it came from half way up the hill, this would signify all was well, but from the top of the hill it would signify danger.

Smoke signals are still in use today. In Rome

Rome

Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...

, the College of Cardinals

College of Cardinals

The College of Cardinals is the body of all cardinals of the Catholic Church.A function of the college is to advise the pope about church matters when he summons them to an ordinary consistory. It also convenes on the death or abdication of a pope as a papal conclave to elect a successor...

 uses smoke signals to indicate the selection of a new Pope

Pope

The Pope is the Bishop of Rome, a position that makes him the leader of the worldwide Catholic Church . In the Catholic Church, the Pope is regarded as the successor of Saint Peter, the Apostle...

. Eligible cardinals conduct a secret ballot

Secret ballot

The secret ballot is a voting method in which a voter's choices in an election or a referendum are anonymous. The key aim is to ensure the voter records a sincere choice by forestalling attempts to influence the voter by intimidation or bribery. The system is one means of achieving the goal of...

 until someone receives a vote of two-thirds plus one. The ballots are burned after each vote. Black smoke indicates a failed ballot; white smoke means a new Pope has been elected.

In general smoke signals are used to transmit news, signal danger, or gather people to a common area.

Yámana

Yámana

Yaghan

The Yaghan, also called Yagán, Yahgan , Yámana or Yamana, are the indigenous inhabitants of the islands south of Isla Grande de Tierra del Fuego extending their presence into Cape Horn...

s used fire to send messages by smoke signals, for instance if a whale drifted ashore. The large amount of meat required notification of many people, so that it would not decay. They might also have used smoke signals on other occasions, thus it is possible that Magellan saw such fires (which inspired him to name the landscape Tierra del Fuego

Tierra del Fuego

Tierra del Fuego is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of a main island Isla Grande de Tierra del Fuego divided between Chile and Argentina with an area of , and a group of smaller islands including Cape...

) but he may have seen the smoke or lights of natural phenomena.

Noon Gun

Noon Gun time signalling was used to set marine chronometer

Marine chronometer

A marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation...

s in Table Bay

Table Bay

Table Bay is a natural bay on the Atlantic Ocean overlooked by Cape Town and is at the northern end of the Cape Peninsula, which stretches south to the Cape of Good Hope. It was named because it is dominated by the flat-topped Table Mountain.Bartolomeu Dias was the first European to explore this...

.

Australian Aborigines

Australian Aborigines

Australian Aborigines

Australian Aborigines , also called Aboriginal Australians, from the latin ab originem , are people who are indigenous to most of the Australian continentthat is, to mainland Australia and the island of Tasmania...

would send up smoke to notify others of their presence, particularly when entering lands which were not their own. However, these were not complex signals; smoke simply told others where one was located.