There are two Tide Predicting Machines in the exhibition – the Doodson-Légé machine and the Roberts-Légé machine. Both of these machines spent their working lives at predecessors of the National Oceanography Centre: the Liverpool Tidal Institute and at Bidston Observatory.

These two machines, and also a third (the so-called ‘Bidston Kelvin machine’, which is now in France), were operated at Bidston Observatory, which at one time produced two-thirds of the world's tide tables. Two of these machines (the Roberts-Légé and Bidston Kelvin machines) played an important part in providing tidal predictions during World War II. The Doodson-Légé machine was acquired by Bidston in the 1950s.

Both the Roberts-Légé and Doodson-Légé machines have been out of use since Bidston switched over to the use of digital computers to make tidal predictions in the 1960s. Eventually, the machines were transferred from Bidston to National Museums Liverpool. Restoring them to their former glory during 2013–2015 was a task carefully undertaken by conservation specialists from National Museums Liverpool. Once restored in August 2015 they were brought to the National Oceanography Centre in Liverpool for display to the public at their ‘spiritual home’.

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The Roberts-Légé Machine.

The Roberts-Légé Machine (British Tide Predictor No. 5) can be seen in the exhibition. Built in 1906–1908 by Légé and Co., London.

This machine was designed by Edwards Roberts, called the ‘Universal Tide Predictor’ and used for his own commercial use. It won the ‘Grand Prix’ of the Franco-British Exhibition of 1908.

It was transferred to Arthur Doodson at the Bidston Observatory in 1929 at a cost of 753 pounds and 15 shillings and refurbished by him.

This is one of two machines (the other being the Bidston Kelvin Machine, TPM-S14) that were used for tidal predictions during World War II.

NameTPM-S5 Bidston Roberts-Légé Machine (British Tide Predictor No. 5)
Manufactured byLégé and Co., London
Manufacture date1906–1908
Architecture typeUnique
Refurbishment1929 and 1936 at Bidston and by National Museums Liverpool 2015
Number of constituents simulated33 + 7
FeaturesGraphical recorder, counter display (later addition)
Present ownerNational Museums Liverpool (2015)
Present locationNational Oceanography Centre, Liverpool, UK
Present working conditionDisplay only, not working.
On display to publicBy arrangement with NOC, Liverpool

The Doodson-Légé Machine.

The Doodson-Légé Machine (TPM-S20) can be seen in the exhibition. Built in 1950 by Légé and Co., London.

The purchase of this machine was initiated when Arthur Doodson asked Mr Jebson (Managing Director of Légé and Co.) to estimate the cost of a new machine with 35 or more constituents. The new machine was delivered to Bidston in December 1950 at a cost of 5,049 pounds.

It was of immense importance to Bidston Observatory, having provided predictions for up to 180 ports worldwide every year.

The Doodson machine is run every now and then to ensure it remains in perfect working order. The accuracy of the predictions it produces now is as good as it ever was.

The digital computers that calculate tidal information today actually use the same fundamental mathematics as the machines do. By comparing results obtained through both methods, the level of accuracy achieved with the TPM is still very impressive.

NameTPM-S20 Bidston Doodson-Légé Machine
Manufactured byLégé and Co., London
Manufacture date1950
Architecture typeRoberts-Légé
Refurbishment2015 by National Museums Liverpool
Number of constituents simulated42
FeaturesGraphical recorder, counter display.
Original operation locationBidston Observatory, Wirral, UK
Present ownerNational Museums Liverpool (2015)
Present locationNational Oceanography Centre, Liverpool, UK
Present working conditionThe machine is in a good working condition suitable for demonstrations to the public, etc.
On display to publicBy arrangement with NOC, Liverpool

The Bidston Kelvin Machine.

This machine is not part of the Tide & Time exhibition, but used to be housed at Bidston Observatory. It is one of two machines that was used for tidal predictions during World War II. The machine was transferred from Bidston to Service Hydrographique et Océanographique de la Marine (SHOM) in 1950 and was operated at their headquarters in Paris. It is now to be found at SHOM in Brest.