Articles

Finding the Amplitudes and Phases to use for the Bidston Tide Prediction Machines

Philip Woodworth, 23 May 2017

There is a lot of renewed interest in tide prediction machines and, after many years hidden away in storerooms, some of the machines made in the UK are on permanent display once again. Kelvin’s original 10-component machine is now part of the new Winton Gallery for Mathematics at the Science Museum in London alongside Ishiguro’s storm surge simulator. Two of the machines that were used at Bidston can now be seen at the National Oceanography Centre building in Brownlow Street in Liverpool.

As you may know from articles mentioned in the Resources section of this web site, the tide prediction machines were a way of simulating the tide in terms of its many harmonic components. Each component would be represented by an amplitude and phase lag, called the ‘harmonic constants’, and the machine, which can be considered as a sort of analogue computer, would be programmed to run by providing it with these constants. Of course, the constants would differ from port to port.

That raises the obvious question of where people like Arthur Doodson, and the other operators of the machines, got their constants from in the first place. This short article reviews the main characteristics of one of the machines (the so-called Doodson-Légé machine now on display at NOC) and then attempts to answer the question of how Doodson obtained the constants.

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Tide & Time Exhibition opens

The Tide & Time Exhibition  is now open to the public.

The exhibition – at the National Oceanography Centre in Liverpool – showcases some of the fascinating achievements made in the Liverpool area in understanding and predicting the tides. The highlights of the exhibition are the rare Roberts-Légé and Doodson-Légé tide prediction machines, extraordinary analogue computers that calculate the rise and fall of the ocean tide. See these beautifully intricate machines up and running at the only place in the world where you can see two of them together.

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My early life at Bidston Observatory

Joyce Scoffield

Originally, from 1955, I worked in the Met Office at Speke Airport (later to be called Liverpool Airport and subsequently John Lennon Airport). I very much enjoyed being a weather observer – sending observations up to the control tower to be passed on to aircraft, but the job involved shift work, which included regular night duties. This was fine till I got married in 1961. At that stage, I became less enthusiastic about shift work and about the amount of travelling involved between Greasby and the airport: bus – ferry – bus – at least an hour each way. I didn’t drive in those days.

So I decided to look for another job. Bidston Observatory came to mind. It was much nearer home and I knew they had a weather station there. So I wrote to the Director asking him if there were any job vacancies. He – Dr. Rossiter – invited me to go for interview and duly offered me a job! It was as easy as that in 1961. Nowadays, with high competition for every post, people can’t believe that it could ever be that easy.

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Reflections on Time

Kevin F. Taylor

I was recently invited to attend a garden party to celebrate 150 years of the Bidston Observatory, hosted by Stephen and Mandy Pickles on Saturday 17 September 2016 in the grounds of Bidston Lighthouse. This gave me a deep sense of déjà vu, as it reminded me so much of my first day as a member of Bidston staff at the start of 1972.

On that day, I drove up the same well-worn drive, past the sandstone wall entrance, and into the grounds. On my right hand side was a lawn that was shortly to be occupied by the new Proudman Building. But in early 1972 that area looked almost the same as it does now, except for a small vegetable patch that was attended to by a Mr. Connell. He and his family occupied the cottages that belonged to the lighthouse and had been built by the Mersey Docks and Harbour Board. On that balmy Saturday evening in September, I thought it quite strange that, here I was celebrating 150 years of the Observatory, and yet the ‘new’ Proudman Building had been built and demolished (in early 2013) within little more than 40 years, a fraction of the Observatory’s lifetime.

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Earth Tides and Ocean Tide Loading

Trevor F. Baker, 2 November 2016

Research on Earth tides and ocean tide loading has an even longer history at Bidston Observatory than the work on ocean tides. This article gives a brief overview of the developments in these research areas following the measurements at Bidston in 1909 by John Milne, with particular emphasis on the contributions of the research groups at Bidston to the advances in these topics.

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Directing Bidston

Graham Alcock, 21 October 2016

I joined Bidston in 1972 and took early retirement in 2000, having survived five name changes (Institute of Coastal Oceanography and Tides, Institute of Oceanographic Sciences, Proudman Oceanographic Laboratory, Centre for Coastal and Marine Science and back to the Proudman Oceanographic Laboratory). Here are anecdotes about some of the Directors during that time.

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Bidston recollections

John Huthnance, 7 Oct 2016.

I joined IOS Bidston (as it was then) in October 1977. The validity of my appointment could be questioned as the appointment letter came from DB Crowder (the Bidston administrator) who left before I arrived.

It was a good time to join. There were about 80 staff in total, few enough to give a “family” atmosphere with the feeling that everyone knew everyone else. Several colleagues had been taken on during the early 1970s but it was still a time of expansion rather than otherwise.   Scientists like myself had a fairly free hand to pursue promising lines of research within a fairly broad remit. I enjoyed a feeling of support from fellow scientists to do just this. Much of the funding came through a consortium of several government departments with an interest in our research. The negotiations were at some distance from most of the scientists who did not have to spend much time writing proposals, yet it was good to know of “user” interest in our work, always a characteristic of Bidston science. It was still possible to be “the” expert in a topic, a rarity today. I was lucky.

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A brief history of Bidston Observatory

Bidston Observatory was built in 1866, when the expansion of Waterloo Dock forced Liverpool Observatory to re-locate to Bidston Hill. It was built alongside Bidston Lighthouse and Signals Station, on land owned by the Mersey Docks and Harbour Board. George Fosbery Lyster was the architect.

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Tidal Curiosities – The Whirlpool of Corryvreckan

Judith Wolf, 1 Sep 2016.

Most people know that the tide rises and falls periodically at the coast but not everyone is as aware of the periodic flood and ebb of tidal currents. These are of particular importance for mariners and need to be taken into account for navigation. Where currents become particularly strong, they can become known as a ‘tidal race’, which can be unnavigable at certain states of the tide.

Around the coast of the British Isles are many locations where a tidal race forms, usually in a constricted channel between two islands or an island and the mainland. In Scotland, between the islands of Jura and Scarba is the famous ‘Whirlpool of Corryvreckan’ – possibly the third largest whirlpool in the world (after Saltstraumen and Moskstraumen, off the coast of Norway). The Gulf of Corryvreckan, also called the Strait of Corryvreckan, is a narrow strait between the islands of Jura and Scarba, in Argyll and Bute, off the west coast of mainland Scotland.

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Tide and Storm Surge Modelling at Bidston Observatory

Philip L. Woodworth, 4 August 2016.

One of the main objectives of the research at Bidston Observatory was to understand more about the dynamics of the ocean tides, that is to say, the physical reasons for why the tide propagates through the ocean as it is observed to do. Before the advent of digital computers, the only way to approach these questions was from basic mathematical perspectives, in which eminent scientists such as Pierre-Simon Laplace in France excelled in the 19th century, and in which Joseph Proudman at Bidston was an acknowledged expert in the 20th century.

Similarly, there has always been considerable interest in the reasons for large non-tidal changes in sea level, including in particular those which occur due to the ‘storm surges’ generated by strong winds and low air pressures in winter. For example, following the Thames floods of January 1928, Arthur Doodson at Bidston chaired a committee for London County Council that undertook a detailed study of the reasons for the storm surge that caused the flooding, and made recommendations for protecting the city in the future.

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