Hydraulic telegraph

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.

[1] Although the British device could be used in any visibility within its range of operation, it could not work in freezing temperatures without additional infrastructure to heat the pipes.

In The Histories, Polybius wrote:[2] Aeneas, the author of the work on strategy, [writing] to find a remedy for the difficulty, advanced matters a little, but his device still fell far short of our requirements, as can be seen from his description of it.

When this is done it is evident that, the conditions being precisely similar, in proportion as the water escapes the two corks will sink and the rods will disappear into the vessels.

This will be the message delivered, if the apparatus works at the same pace in both cases.Modern experiments show that the data transfer rate can achieve 151 letter per hour.

It appears to us that the amount of information which can be conveyed by the motion in one direction only, of the water, or backward and forwards, must be limited.

To make the mere motion backwards and forwards of a float board, indicated on a graduated index, convey a great number of words or letters, is the difficulty to be overcome.The article concluded speculatively that the "... hydraulic telegraph may supersede the semaphore and the galvanic telegraph".