Hydraulic telegraph
Encyclopedia
A hydraulic telegraph was one of two hydraulic-telegraphic telecommunication
systems, one developed in 4th century BCE Greece
, and the other in 19th century AD Britain
. The Greek system was deployed in combination with semaphoric
fires, while the latter British system was purely hydraulic.
Although both systems employed water in their sending and receiver devices, their transmission media were completely different. The ancient Greek system transmitted its semaphoric information to the receiver visually, which limited its use to line-of-sight distances in good visibility weather conditions only. The 19th century British system used water-filled pipes to effect changes to the water level in the receiver unit (similar to a transparent water-filled flexible tube used as a level indicator), thus limiting its range to the hydraulic pressure that could be generated at the transmitter's device.
While the Greek device was extremely limited in the codes (and hence the information) it could convey, the British device was never deployed in operation other than for very short-distance demonstrations. The British device could, however, be used in any visibility within its range of operation so long as its conduits, if unheated, did not freeze in sub-zero temperatures —which contributed to its impracticality.
and the 3rd century BC by the historian Polybius
. According to Polybius, it was used during the First Punic War
to send messages between Sicily
and Carthage
.
The system involved identical containers on separate hills; each container would be filled with water, and a vertical rod floated within it. The rods were inscribed with various predetermined code
s at various points along its height.
To send a message, the sending operator would use a torch to signal the receiving operator; once the two were synchronized, they would simultaneously open the spigots at the bottom of their containers. Water would drain out until the water level reached the desired code, at which point the sender would lower his torch, and the operators would simultaneously close their spigots. Thus the length of time the sender's torch was visible could be correlated with specific predetermined codes and messages.
A contemporary description of the ancient telegraphic method was provided by Polybius. In The Histories
, Polybius wrote:
Francis Whishaw, who latter become a principal in the General Telegraph Company, publicized a hydraulic telegraph in 1838 but was unable to deploy it commercially. By applying pressure (or a negative pressure vacuum) at a transmitter device connected to a water-filled pipe which travelled all the way to a similar receiver device, he was able to effect a change in the water level which would then indicate coded information to the receiver's operator.
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
systems, one developed in 4th century BCE Greece
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
, and the other in 19th century AD Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
. The Greek system was deployed in combination with semaphoric
Semaphore
A semaphore telegraph, optical telegraph, shutter telegraph chain, Chappe telegraph, or Napoleonic semaphore is a system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the...
fires, while the latter British system was purely hydraulic.
Although both systems employed water in their sending and receiver devices, their transmission media were completely different. The ancient Greek system transmitted its semaphoric information to the receiver visually, which limited its use to line-of-sight distances in good visibility weather conditions only. The 19th century British system used water-filled pipes to effect changes to the water level in the receiver unit (similar to a transparent water-filled flexible tube used as a level indicator), thus limiting its range to the hydraulic pressure that could be generated at the transmitter's device.
While the Greek device was extremely limited in the codes (and hence the information) it could convey, the British device was never deployed in operation other than for very short-distance demonstrations. The British device could, however, be used in any visibility within its range of operation so long as its conduits, if unheated, did not freeze in sub-zero temperatures —which contributed to its impracticality.
Greek hydraulic semaphore system
The ancient Greek design was described in the 4th century BC by Aeneas TacticusAeneas Tacticus
Aeneas Tacticus was one of the earliest Greek writers on the art of war.According to Aelianus Tacticus and Polybius, he wrote a number of treatises on the subject. The only extant one, How to Survive under Siege , deals with the best methods of defending a fortified city...
and the 3rd century BC by the historian 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...
. According to Polybius, it was used during the First Punic War
First Punic War
The First Punic War was the first of three wars fought between Ancient Carthage and the Roman Republic. For 23 years, the two powers struggled for supremacy in the western Mediterranean Sea, primarily on the Mediterranean island of Sicily and its surrounding waters but also to a lesser extent in...
to send messages between Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
and Carthage
Carthage
Carthage , implying it was a 'new Tyre') is a major urban centre that has existed for nearly 3,000 years on the Gulf of Tunis, developing from a Phoenician colony of the 1st millennium BC...
.
The system involved identical containers on separate hills; each container would be filled with water, and a vertical rod floated within it. The rods were inscribed with various predetermined code
Code
A code is a rule for converting a piece of information into another form or representation , not necessarily of the same type....
s at various points along its height.
To send a message, the sending operator would use a torch to signal the receiving operator; once the two were synchronized, they would simultaneously open the spigots at the bottom of their containers. Water would drain out until the water level reached the desired code, at which point the sender would lower his torch, and the operators would simultaneously close their spigots. Thus the length of time the sender's torch was visible could be correlated with specific predetermined codes and messages.
A contemporary description of the ancient telegraphic method was provided by Polybius. In The Histories
The Histories (Polybius)
Polybius’ Histories were originally written in 40 volumes, only the first five of which are existent in their entirety. The bulk of the work is passed down to us through collections of excerpts kept in libraries in Byzantium, for the most part....
, Polybius wrote:
British hydraulic semaphore system
The British civil engineerCivil engineer
A civil engineer is a person who practices civil engineering; the application of planning, designing, constructing, maintaining, and operating infrastructures while protecting the public and environmental health, as well as improving existing infrastructures that have been neglected.Originally, a...
Francis Whishaw, who latter become a principal in the General Telegraph Company, publicized a hydraulic telegraph in 1838 but was unable to deploy it commercially. By applying pressure (or a negative pressure vacuum) at a transmitter device connected to a water-filled pipe which travelled all the way to a similar receiver device, he was able to effect a change in the water level which would then indicate coded information to the receiver's operator.