Tide and Time – a history of tidal science in Liverpool

This short film, by Andy Lane, Andy Heath and Craig Corbett, is part of the Tide and Time exhibition at the National Oceanography Centre, Liverpool. The exhibition showcases two tidal prediction machines – the Roberts-Légé and the Doodson-Légé. The film also explores the history of tidal science in Liverpool and its development as a port.

Enjoy!

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.

Bidston Observatory was the home of the Roberts-Légé and Doodson-Légé tide prediction machines while they were still in use. The machines are now owned by National Museums Liverpool, who have carefully restored them to working condition.

Tide & Time is open to the public once a month (usually the first Tuesday of each month from 15:00 to 16:00) or by special arrangement for group visits and events. See this page for information on planning your visit and how to book.

The exhibition will also be open to the public during LightNight Liverpool on Friday 19th May 2017 from 17:00 to 22:00.

The Doodson-Légé machine in the 1990s in the reception area of the Proudman Oceanographic Laboratory. The machine is now on display at the National Oceanography Centre in Liverpool.

 

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.

I was a very basic assistant at Bidston – one of 10 girls who were classed as ‘computers’. We operated tidal prediction machines – large machines consisting of gears, weights and pulleys which could be set to represent the contributions of sun, moon, location, etc. to the tides of a port. You can read all about these machines in other articles on this site.

The scientific programs which turned these numbers into tidal predictions were written by the scientists – them upstairs! – it was all way beyond our understanding. We just operated the machines by foot pedals and a hand wheel and wrote down the answers – the more senior girls scanned our numbers looking for obvious errors. When plotted on a graph, the figures would form a smooth curve representing the pattern of the tide on consecutive days at the port concerned. Once the figures had been accepted as correct, we had to write them down on prepared forms – using pen and ink – no biros allowed – neat handwriting was essential for the job! There was a darkroom in the basement where our carefully written-out tables were photographed before being sent to the port authority concerned. This was a typically old-fashioned dark room with trays of chemical developers, subdued red lights, etc. In those days we did tidal predictions for many parts of the Commonwealth.

Another of the girls’ duties was to maintain a daily weather diary. At 9 am each day – Saturdays, Sundays and Christmas Day included – the duty observer would take readings from the thermometers in the Stevenson’s Met. Screen sited on the Observatory lawn, change the temperature and humidity charts on the analogue instruments also sited in the met screen and change the chart in the tipping bucket rain gauge, as well as measuring any rainfall recorded in the rain bottle. The observer would then go up to the roof to change the daily sunshine card in the Campbell-Stokes sunshine recorder. The sun’s rays were concentrated through a solid glass ball to produce a burn on the specially-treated card. In the summer, this recorder was located on the roof of the ‘Dines cabin’ – the climb up the ladder to this site could be rather precarious on a windy day. In winter, the sunshine recorder was moved to the outside of one of the domes accessed from inside the dome by a small door (again up steps) facing due south. Because the sun is a lot lower in the sky in winter, and needing a smaller range of exposure, this was obviously safer for the staff than the outside summer climb.

Inside the ‘Dines cabin’ was the Dines anemometer recording wind speed and direction on an analogue chart. There again the observer changed the chart on the instrument’s cylinder. The final job was to note the visibility from all sides of the roof. On fine days, we had a great view over Liverpool with the Pennines in the distance. To the north, we could see Blackpool and occasionally Black Coombe in Southern Scotland. To the west, we could see the Great Orme and the Snowdonia range.

Taking the retrieved charts and the sunshine card, the observer returned to the office and calculated three hour readings for the past 24 hours and entered them into the weather diary. These diaries were beautifully produced for us by a company in Liverpool and, I believe, they are now housed in the Wirral Libraries Archive in the Cheshire Lines Building in Birkenhead.

Photo of the One O'Clock Gun, still sited in Birkenhead
The One O’clock Gun is still sited in Birkenhead

Another job for the duty observer was to fire the one o’clock gun at precisely 1 pm Mondays to Fridays. This was a tradition dating back to the building of the Observatory in 1866, when accurate time was not available to the business people of Liverpool. A very accurate clock in the Observatory was connected by landline to a gun sited at Morpeth Dock, on the Birkenhead side of the Mersey. When the observer flicked a switch at Bidston the gunfire was heard in Liverpool (the gun having first been duly primed by a docker at Morpeth). The practice was discontinued at Bidston in 1969, but still continues at observatories in other parts of the world.

The girls had little association with the scientists who were mostly men. At coffee time – strictly 1045-1100 am (we daren’t overstay our time limit) – the men stood round the marble fireplace in the old dining room and the girls sat at the tables. There was little communication between the two groups. Incidentally, the girls prepared the coffee on a rota bases – strictly 50% warm milk – heated in a pan and 50% water. When the coffee was ready, spot on 1045 am, we pressed a buzzer – I think it was 2 buzzes for coffee break – to summon the staff from upstairs.

At lunch time, on a fine day, the menfolk would often take a brisk walk over Bidston Hill usually talking shop. The girls tended to sit on the observatory front door step eating their sandwiches.

It was quite a hierarchical situation at the observatory in those days – a total staff of only about 18 people – a sort of strict family atmosphere – and always quiet. I enjoyed working there.

When I was expecting my first baby in 1964, people seemed quite relieved. It was several years since anyone had become a mum and they had thought there was a hoodoo on the place! Dr. Rossiter was very solicitous towards me when I became pregnant – he insisted on my desk being moved downstairs to save me having to climb anywhere or do anything at all strenuous. There was no thought of my returning to work after having the baby. Mums did not return to work in those days! In the event, I did return to Bidston part time when my younger son was nine years old and attitudes towards working mums were starting to ease.

More stories of life at Bidston Observatory at this time can be found in my book “Bidston Observatory: The Place and the People” (Countryvise Ltd. 2006. ISBN: 978190121687).

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.

The nostalgia continued as I parked my car behind the rear of the Observatory in almost the same spot as I had on that first day at work. I remembered thinking back; my father would quite often force me to join him on one of his marathon walks. One of his favorite treks was from Moreton to Bidston, then over the Vyner Road footbridge, past the windmill, around the Observatory boundary wall down to the village, then home. In the 1950s and early 60s, I was infatuated by science fiction and men-from-outer-space movies, and TV dramas like Quatermass and Doomwatch. For me, looking over the walls surrounding the Observatory presented all kinds of mysteries: What secrets were hidden inside the huge white domes? My youthful and vivid imagination had no bounds in ‘them days’.

On my first day in 1972, I now had the chance to look at the Observatory from the inside out, as opposed to the outside in. How exciting! As I got out of my car and approached the entrance, a gentleman in front of me held the door open and greeted me with the words “Hello Kevin, glad to see you are joining us”. We then passed through the vestibule door and continued to chat in the hallway for a good ten minutes. He then finished by saying “you will be with Dr. Skinner’s group. I will take you to his office”. He gave a quick knock on the door, popped his head around, and said “Sorry Len, Kevin is not late, my fault I kept him chatting”. I was later taken through to the rear of the building for the mid-morning tea break when the same gentleman entered. I turned to one of the staff and asked “who the nice man was”. “That is Dr. Rossiter our director” was the reply. I was then informed that he was the brother of that brilliant actor Leonard Rossiter from the Rising Damp and Reginald Perrin television shows (come to think of it, they did look alike). [Editor’s Note: see mention of Rossiter and other Bidston Directors in an article by Graham Alcock].

So, allow me to digress about a couple of things that have struck me about time, and why I have given the title of this article as ‘Reflections on Time.’ It seems to me that we have different perceptions of time depending on the situation. For example, my first day at the Observatory was over forty years ago, and yet on that recent Saturday in September, it felt like only yesterday. Another example concerns my grandmother, who was 104 years of age when she passed away. When she was born in 1889, the Observatory building had been completed (in 1866) only 23 years before. So, why were we so concerned with celebrating the Observatory as an ‘historic building’, when my memories of my grandmother do not feel ‘historic’? She was just my Nan. So, time is a funny business.

One of the main reasons for the Observatory was to provide accurate time. This gives me a chance to refer to a hero of mine called John Harrison, who had nothing to do directly with the Observatory but, of course, also had an important role in our maritime history. When a fleet of warships ran aground with the loss of many lives and ships due to bad navigation, a vast reward was offered by the King to anybody who could come up with a good way to improve navigation at sea. The main problem was how to calculate longitude, and many ideas were offered: for example, a crazy scheme for anchoring old redundant ships at fixed positions apart, distributed across the whole ocean. The establishment was convinced that the only way that longitude could be calculated, was by using the stars and planets. Harrison in the meantime concentrated on trying to develop a precision marine chronometer. His theory, that longitude could be calculated by the use of time to good precision, was treated with great disdain.

To prove his theory, he would be entirely dependent on producing an accurate timepiece. This proved to be a formidable task. Not only had it to overcome a ship’s movement, but temperature played a significant part in the reliability of the timepieces he produced. Originally, clocks used a pendulum and weight with an escapement movement, but temperature would increase and decrease the length of the pendulum, making the precision he was looking for unsatisfactory. He spent many years trying to overcome this, by making the pendulum out of metal rods with different thermal coefficients of expansion, but alas to no avail. It was not until the latter part of his life that he produced the famous Harrison timepiece. The connection to the Observatory in this story is, of course, that the calibration of marine chronometers was subsequently to form an important part of activities at Bidston, in addition to the astronomical work in establishing the longitude of the port of Liverpool.

Accurate time has historically not been very important for most ordinary people – the sun came up, the sun went down, and what happened in between was neither here nor there. However, for those people who did need accurate timing (on land), the development of affordable watches and clocks, supplemented by sundials, was enabling decent and routine measurements of time by the end of the 18th century. One way of providing accurate timing information to the general population was by the use of time balls controlled by nearby observatories such as Bidston. A time ball was a large sphere (a ball) on top of a shaft positioned on the roof of a prominent building. At precisely midday (or another time such as 1 pm), the sphere would be dropped and people (including ships’ captains) would set their watches. This was a satisfactory situation only when visibility due to the weather allowed the time ball to be seen. Instead, the time balls were eventually complemented by an audible signal such as made by a canon. Hence, the famous Liverpool “One O’clock Gun” came into being. Originally the Liverpool Observatory was located at Waterloo Dock, and the gun (a remnant of the Crimean War) was fired from the Liverpool side of the Mersey. An improvement was made by moving the Observatory from Liverpool to the highest point on the Wirral side of the river, but close to the Dock Estate, this being Bidston Hill. The gun was relocated to Morpeth Dock in Birkenhead, and was now fired directly by an electrical signal from the Observatory.

Time eventually became a significant factor in everyone’s life, and now controls our lives more and more. Everyone knows about the advent of the industrial revolution, and the development of the railway, and the national adoption of Greenwich Mean Time. Now we are controlled by our smart-phones by time that comes from space via GPS satellites. Everyone is in a hurry or we’ll be ‘late’.

So I have been thinking back to that first day at work. At that time, I had many questions, such as “Why is the Observatory called The Institute of Coastal Oceanography and Tides, or ICOT for short?” Or, “What has oceanography got to do with astronomical observations?” These questions were answered for me over the years as I got to understand the relationships between the heavens and earth, and in particular the relationships between time and the tides, and so the ocean, and how these topics have evolved to become a crucial part of everyday life.

This has been a very brief look, from my perspective, at ‘time’ and at some small aspects of life at Bidston Observatory. It would take many volumes to do it justice to it regarding topics such as the development of tide tables, the use of precise instruments (e.g. for earth tides), the collection of oceanographic data from around the world, the fieldwork at many locations etc. Perhaps other people can cover these topics on this web site. Some of the world’s most famous oceanographic scientists have worked at or passed through the Observatory during its history. I feel very fortunate to have experienced a small part of the wealth of that Bidston history. And I hope that its historical significance is appreciated by future generations.

 

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.

I only met ICOT’s Director, Jack Rossiter, when he was chair of my interview panel in May 1972, because unfortunately he died before I was appointed. The subsequent ICOT Acting Director, Geoff Lennon, had a turn of phrase – “it occurs to me” – and that was used in my letter of appointment, suggesting that I might like to join a scientific cruise in September 1972, pre-dating my actual appointment date of 1 October. What Geoff omitted to say was that the cruise was on the RRS John Murray, an ex-fishing trawler rumoured to have been bought by NERC for £1, which had such a nasty rolling motion in anything higher than a Force 2 breeze that it was always difficult to encourage Bidston staff to go on it. That was my introduction to “wet” oceanography – subsequently I always preferred the “dry” oceanography remotely carried out by land-based radar and space-borne satellites.

The first of the frequent reorganisations of NERC’s marine science occurred in 1973, when Bidston became part of IOS, together with what had been the National Institute of Oceanography at Wormley and the Unit of Coastal Sedimentation at Taunton. Scientific rationalisation brought the Tides staff at Wormley to Bidston and David Cartwright was appointed as IOS Assistant Director.

David was a world-class researcher and an elected Fellow of the Royal Society; but as he said on his interview for The British Library’s “Voices of Science”, he “wasn’t temperamentally suited to getting too much involved with administration”. I remember attending an IOS meeting at Wormley to allocate funding for the year (in my capacity as responsible for contracted and commissioned research at Bidston), when David left early to catch his train back to Birkenhead before Bidston finances had been fully discussed and agreed. James Crease said: “I suppose we had better allocate some funds to Bidston”.

I worked on a number of projects for David and although he was the senior author of our joint papers he used the format of listing the authors in alphabetical order. For the George Deacon 70th Birthday commemorative volume of “Deep Sea Research”, we wrote a paper on our analysis and interpretation of telephone cable voltages across the English Channel to provide information on the ocean current flow. The DSR Editor knew of David but not me, and on his assumption that the first named author was the senior author, his acceptance letter (no emails then) to us was addressed to Professor Alcock; much to our amusement.

Another project that I worked on with David was the analysis of data from SEASAT – the first satellite dedicated to oceanography. In the 1970s, our visit to Venice for a SEASAT Workshop enabled David to indulge in two of his passions: railways (Liverpool – London – Calais – Venice is some train ride) and wine (his wife was French). A very good bottle consumed by us on the return rail journey was paid for using a pile of Italian Lire left over when we had discovered that our Hotel accommodation had been paid by the Workshop organisers.

After our successful campaign in the late 1980s against Bidston’s closure and transfer to Wormley, Bidston became autonomous and was renamed the Proudman Oceanographic Laboratory. (The IOS Taunton site was closed and staff transferred to Bidston or Wormley.) Brian McCartney was appointed POL Director and, in my opinion, the next eight years were Bidston’s halcyon days: we reported directly to NERC HQ, without an intervening level of bureaucracy of IOS or later CCMS or NOC.

Brian always let Group and Project leaders have a full say at the Management Committee; especially at the annual allocation meeting (consequently it sometimes went on for two days); so I felt that if you inevitably didn’t get all the money or equipment that you had bid for, you still accepted his final decisions because you had had a fair hearing. Brian was also careful to include all “Prime-movers” (the researchers) in the vision and major decisions that directed our strategy. In those ways, I believe that he made sure that all staff felt that they had had some input in formulating the strategy that POL took under his Directorship, with ensuing collective responsibility and underpinning the Bidston “family” atmosphere that John Huthnance mentions in his article.

Brian had been Head of the Engineering Group at Wormley, so it was not surprising that technology development at Bidston thrived during his Directorship. Bidston became one of the few European laboratories with the capability of developing and deploying oceanographic instruments in the coastal zone, shallow or deep water. Together with our expertise in the analysis and interpretation of the data and the world-class hind-casting and fore-casting modelling expertise developed under Norman Heaps’ leadership, Bidston’s scientists and engineers were in great demand for European Community/Union oceanography projects. Not bad for an organisation later accused of scientific isolation because it was on a hill five miles away from Liverpool University.

Under Brian’s leadership, POL became the host laboratory for the North Sea Project, the first large “Community Research Project”, involving many other research institutes and university research departments. We developed a strategy of funding all our Laboratory Science and Technology Projects from a triple combination of Commissioned Research (mainly from the DoE, MAFF and MoD), EC/EU Programmes and the NERC Science Budget; giving us some financial stability.

Happy days!

With the movement of IOS Wormley to Southampton University in the 1990s, NERC carried out yet another reorganisation of its marine science, lumping its remaining oceanographic laboratories at Bidston, Oban and Plymouth, into a “Centre” for Coastal and Marine Science. Jackie McGlade was appointed to what I always considered was a poisoned chalice of a job as the CCMS Director. (CCMS was disbanded in 2000, the then NERC Chief Executive admitting that the CCMS experiment had failed.) Jackie faced a fair degree of hostility from some senior staff, particularly at Plymouth where her office was situated, as staff at the three previously autonomous laboratories tried to work out what exactly was the purpose of the “Centre”.

I worked closely with Jackie on aspects of commissioned research and scientific applications across CCMS and got on well with her. She tended to be quite open about what she felt (perhaps that’s what some senior CCMS staff didn’t like) and because of this I was probably the first Bidston staff member to find out about the proposed closure of Bidston and transfer to Liverpool; a decision that had been taken by the then Bidston Director, without, as far as I know, any consultation with Bidston staff (the Management Committee had been an early casualty of his appointment.) Jackie and I were travelling on the London Underground, back from a meeting with an Intellectual Property lawyer, when Jackie asked me what I thought about the plan to close Bidston and move everyone to Liverpool University. I was non-committal.

Frank Field, MP for Birkenhead, had been a main factor in NERC’s decision not to close Bidston in the 1980’s and I informed him of the decision. I was summoned to the Bidston Director’s office and told, in no uncertain terms, that he was the Director and made the decisions, which I had to obey as a member of his staff without discussion. I demurred. I took early retirement in 2000, having thoroughly enjoyed most of the time at Bidston and working for most of the Directors.

(The British Libraries’ “Voices of Science” is at http://www.bl.uk/voices-of-science/interviewees. As well as David Cartwright, other oceanographers interviewed are James Cease, Anthony Laughton, John Woods and Philip Woodworth.)

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.

Everyone was expected to go to sea at least once. My first experience was a long trip in October 1978 on RRS Discovery from South Shields to Recife (Brasil)! We had calm across the Bay of Biscay but gradually increasing seas as time progressed. Green terminal screens on board added to my discomfort. It also got hot enough to affect some of the electronics and the salinometer bath struggled to maintain any standard temperature. My struggles with the latter resulted in being one of many co-authors on a paper about steric height around the equator – as I discovered when the paper was published.

My next research “cruise” was less exotic, to the North Sea on RRS John Murray. The picture shows the arrangement for under-way surface sampling – a CTD (device for measuring the conductivity and temperature of sea water at a known depth) in a bucket lashed to the side.

Arrangement for under-way surface sampling
Arrangement for under-way surface sampling

I have seen some changes in the “style” of research – some for the better! In the 1980s John Bowman (Chief Executive of NERC) told us that if we wanted students, we should get a university job. Now student supervision is encouraged (and helped by being in Liverpool). When I started, current meter data processing typically involved printing out all the recorded values. Models were semi-analytic or had reduced dimension or coarse resolution. My thesis compared a few tidal harmonic constants between measurements and a simple model. Now we have millions of observed values, billions of model output values, and we need computer programs to translate these to something viewable. In the end, science wants to compare two independent numbers for the same quantity. With the “Big Data” that modern science generates, is it harder to think what we are aiming at?

 

North Sea Project - monthly surveys
North Sea Project – monthly surveys

Another change is towards “inter-disciplinary science”. I have been a believer in this owing to early good experience: a seminar at Bidston by John Allen (University of Reading) about sand transport gave me an idea for how sand banks might grow (I had already published about the character of tidal flow around the Norfolk sand banks). The “flip” side to inter-disciplinarity is the overhead of communication with a wider group of scientists. Anyway, Bidston (now Proudman Oceanographic Laboratory – POL) saw this in a big way in NERC’s first “Community Project”, the North Sea Project (formally 1987-1992). John Howarth and I were respectively coordinators of the monthly “surveys” (see figure) and intervening “process studies” for 15 months in 1988-89. I recall a “spat” with Philip Radford (PML) at the concluding 1993 Royal Society Discussion meeting. I showed a diagram characterised by physics-ecosystem. Philip countered with physics-ecosystem. These are of course quite compatible, differing only by which part is under the microscope.

The North Sea Project was followed by the “Land-Ocean Interaction Study” LOIS in the 1990s with POL at the centre of coastal, shelf-edge and modelling studies. Such large-scale projects with many participants involved a Steering group and many rail trips to London. At the same time (and possibly inspired by NERC) the EU Marine Science and Technology Programme (MAST) began. My main involvement was in “Processes in Regions of Freshwater Influence” (PROFILE; two phases), “Ocean Margin Exchange” (OMEX; two phases) – both inter-disciplinary – and “Monitoring Atlantic Inflow to the Arctic” (MAIA) which somehow managed to be only physics. MAST projects had several European partners; the beaten track became the M56 for Manchester airport and flights to partners’ laboratories, EU Brussels and MAST gatherings in rather nice places (e.g. Sorrento, Vigo, . . ).

After formation of Southampton Oceanography Centre SOC, there was an April 1st announcement setting up the “Centre for Coastal Marine Science” CCMS in the mid-1990s as a counterpart to SOC. CCMS incorporated PML, POL and SAMS and resulted in more trekking, to Plymouth and Oban. This was good for inter-lab communications but management went awry, especially regarding finances, and POL became “independent” again (within NERC) in 2001. 2001 was also the year of design for the new building for POL in Liverpool (pictured). There were several reasons for unhappiness about this; building down to a price, inevitable open-plan offices (being cheaper and set by Swindon precedent), more time and expense of commuting for most staff. I had the “joy” being project “sponsor”. In building procurement this does not mean having the money but rather liaison between the “owner” (NERC with the money) and the design team. I was in the architect’s Birmingham offices on “9/11”.

POL's new building in Liverpool
POL’s new building in Liverpool

After more than a year’s delay on completing the Liverpool building, we finally left Bidston at the beginning of December 2004.

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.

George Fosbery Lyster
George Fosbery Lyster

John Hartnup, astronomer and Assistant Secretary to the Royal Astronomical Society, had been the Director of Liverpool Observatory since it was built in 1843. Amongst his achievements was the calculation of the longitude of Liverpool, which was important for navigation and the development of the port. He presided over the move to Bidston Hill, and continued as director of Bidston Observatory until his retirement in 1885, when he was succeeded by his son. The second director, John Hartnup Jr  died on 21 April 1892, when he fell from the roof of the Observatory while making meteorological observations.

Bidston Observatory and Lighthouse, postmarked 1907
Bidston Observatory and Lighthouse, postmarked 1907

Over the years, the emphasis of the Observatory’s work shifted from astronomy to other things, but always in the tradition of Time and Tide, so important to the port of Liverpool.

Of Time. The progression from observations of the stars, to the determination of longitude, to the calibration of chronometers was a natural one. The Observatory’s two levels of cellars and other features made it especially suited for calibrating chronometers under controlled conditions of temperature and seismic vibrations. Mariners sent their chronometers from all over the empire for calibration at Bidston. The One-O-Clock gun at Morpeth Dock was signalled from Bidston Observatory.

Of Tide. Ever since Liverpool’s harbour-master William Hutchinson (the same fellow who pioneered the use of parabolic reflectors in lighthouses on Bidston Hill) took the first extended series of tidal measurements over a period of nearly thirty years, Liverpool had led the world in tidal studies. This work became centred at Bidston Observatory when the Liverpool Tidal Institute was set up there under Joseph Proudman’s direction after World War I. Arthur Doodson’s work with mechanical computers for tide prediction happened here. One of his machines was used to predict the tides for the D-Day landings.

Observatory staff by the original one-o-clock gun, after its removal to Bidston Hill from Morpeth Dock.
Observatory staff by the original one-o-clock gun, after its removal to Bidston Hill from Morpeth Dock.

In 1969, the Natural Environment Research Council (NERC) took over responsibility for the Observatory. Oceanographic research continued to expand under their auspices. During the 1970’s, the Joseph Proudman Building was constructed in the former kitchen gardens of Bidston Lighthouse.

In 1989, the Observatory, Lighthouse and the perimeter wall enclosing them became Grade-II listed buildings.

In 2004, the Proudman Oceanographic Laboratory moved from Bidston Hill to a new building at the University of Liverpool. Their oceanographic research is still continuing today, but now in the guise of the National Oceanography Centre.

The departure of the Proudman Oceanographic Laboratory from Bidston Hill began a 12-year limbo. NERC’s original plan to sell the site to a developer aroused opposition from local pressure groups, and the spectre of an eleven-story high-rise residential development was averted. In 2012, NERC applied for and obtained planning permission and listed buildings consent (now lapsed) to convert the Observatory into four residential apartments. Later that year, the Joseph Proudman Building was demolished. Having put the Observatory to the market on several occasions, NERC finally sold it in 2015 to a developer (Bidston Observatory Developments Limited), who had outbid a community-led consortium. This was the lowest point in the Observatory’s history. A period of systematic neglect saw a rapid deterioration of the fabric of the building and the appearance of the grounds, exacerbated by water ingress, unpaid bills and a winter with no heating, and the Observatory was nominated to the Victorian Society’s list of the top ten endangered buildings of 2016.

Fortunately, the Observatory was sold again in September of 2016. The new owners have announced their intentions to operate the Observatory as a not-for-profit artists’ research centre and to incorporate an exhibition celebrating the Observatory’s scientific heritage.

 

 

 

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.

These areas of research were revolutionised in the mid-20th century, stimulated by public concerns following the major floods and loss of life in East Anglia in 1953 (Figure 1c,d), and finally made possible by the availability of modern computers in the 1960s. An important person in using computers in this work at Bidston was Norman Heaps, who joined the staff in 1962 and was eventually joined by a group of ‘modellers’ and ‘student modellers’ including Roger Flather, Judith Wolf, Eric Jones, David Prandle and Roger Proctor.

(As a digression, we may also mention the attempted simulation in this period of storm surges using electronic circuits, in effect analogue computers, by Shizuo Ishiguro, the father of the novelist Kazuo Ishiguro, at the Institute of Oceanographic Science at Wormley in Surrey. These devices were made redundant by digital computers. Ishiguro’s equipment can be seen at the Science Museum in London.)

Computer modelling of the tides has many similarities to the modelling of storm surges. In both cases, there are external forces involved: gravitational due to the Moon and Sun in the case of the tides, and meteorological (winds and air pressure changes) in the case of storm surges. These forces are exerted on the water surface inducing currents and redistributing volumes of water.

So the first thing a modeller has to know is how much the forces are. These are provided from astronomy in the case of the tides, and from meteorology for storm surges (e.g. information from the Met Office). In the case of the 1953 storm surge, the effect of the wind can be appreciated from Figure 1(a) which shows a deep depression crossing from west to east and strong winds from the north pushing water into the southern part of the North Sea. The winds are especially important in this case: their force is determined by the ‘wind stress’, which is proportional to the square of the wind speed, and the dynamics are such that a greater surge occurs when wind stress divided by water depth is maximum. In other words, bigger surges occur in shallower waters, such as those of the southern North Sea or the German Bight.

Figure 1. Images from the 1953 North Sea storm surge that resulted in over 2500 fatalities, mostly in the Netherlands and eastern England. (a) Meteorological chart for 1 February 1953 (0 hr GMT) with the track of the storm centre shown by black dots in 12-hour steps from 30 January (0 hr) to 1 February (0 hr); (b) maximum computed surge throughout the area (cm); (c) flooding at Sea Palling on the Norfolk coast of England; (d) the Thames Barrier, an example of the considerable investment in coastal protection in the United Kingdom and Netherlands following the 1953 storm. For image credits, see Pugh and Woodworth (2014).
Figure 1. Images from the 1953 North Sea storm surge that resulted in over 2500 fatalities, mostly in the Netherlands and eastern England. (a) Meteorological chart for 1 February 1953 (0 hr GMT) with the track of the storm centre shown by black dots in 12-hour steps from 30 January (0 hr) to 1 February (0 hr); (b) maximum computed surge throughout the area (cm); (c) flooding at Sea Palling on the Norfolk coast of England; (d) the Thames Barrier, an example of the considerable investment in coastal protection in the United Kingdom and Netherlands following the 1953 storm. For image credits, see Pugh and Woodworth (2014).

The next problem is to determine what the impact of these forces is, and for that the computer solves sets of mathematical equations at each point on a grid distributed across the ocean (e.g. Figure 2); these equations are in fact the same ones that Proudman and others used but could not be applied in this way at the time. The output of the models consists of long records of sea level changes and of currents at all points in the grid: as an example, Figure 1(b) provides a map of the maximum resulting surge during the 1953 storm surge event. Layers of ‘nested models’ enable very detailed information to be provided to coastal users in particular localities.

Figure 2. The grid used for the numerical surge model employed in the current UK operational surge forecasting system. Only a section of the grid is shown to give an impression of model resolution and matching of a finite-difference grid to a coastline. The complete grid covers the entire northwest European continental shelf from 40° to 63° N and eastwards of 20° W. The model is forced by winds and air pressures covering the entire North Atlantic and Europe on a 0.11° grid indicated by dots. From Pugh and Woodworth (2014).
Figure 2. The grid used for the numerical surge model employed in the current UK operational surge forecasting system. Only a section of the grid is shown to give an impression of model resolution and matching of a finite-difference grid to a coastline. The complete grid covers the entire northwest European continental shelf from 40° to 63° N and eastwards of 20° W. The model is forced by winds and air pressures covering the entire North Atlantic and Europe on a 0.11° grid indicated by dots. From Pugh and Woodworth (2014).

As Figure 1 demonstrates, surge modelling is particularly important to people who live at the coast. The Met Office can provide data sets of winds and air pressures up to 5 days ahead, which can be used to force the computer models. And, because the models can thankfully run faster than ‘real-time’, they can provide forecasts of what the likely magnitudes of storm surges will be several days ahead, enabling flood warnings to be issued. In the case of London, the operational warnings can be used to decide whether or not to close the Thames Barrier (Figure 1d).

These forecast techniques, developed at Bidston by Norman Heaps, Roger Flather and others, were first used operationally at the Met Office in 1978, and successor models, which are conceptually the same, are still used there, providing warnings to the Environment Agency. Similar schemes have been adopted by other agencies around the world. Storm surge models developed at Bidston have also been applied to areas such as the Bay of Bengal where surges can be considerably larger than around the UK and where there has been a large loss of life on many occasions.

Modelling at Bidston later developed into studying the 3-dimensional changes in the ocean that result in the transport of sediments or pollutants (‘water quality modelling’) or that have impacts on ecosystems. Modelling has also been applied to topics such as the safety of offshore structures and renewable energy. The same sort of computer modelling is now used throughout environmental science. For example, the models that the Met Office uses for weather forecasting, or the Hadley Centre uses to predict future climate use the same principle of solving physical equations on a grid.

But every modeller knows that their model provides only an approximate representation of the real world, and to help the model along there is sometimes a need to include real measurements into the model scheme, in order to constrain the mathematical solutions on the grid. These are called ‘assimilation models’, of which forecast weather models are the most obvious examples.

This enables us to return to tide modelling. Scientists at Bidston developed many regional models of the ocean tide for engineering applications as well as scientific research. These models tended to have ‘open boundaries’ where the region of the model grid meets the wider ocean. In these cases, it is normal to prescribe ‘boundary conditions’ which specify the tide at the boundary, and which are in effect a form of data assimilation. However, if one wants to make a tide model for a large region or for the whole ocean, with no boundaries, it was found that there were problems with obtaining acceptable results, as the assumptions which go into the computer codes were not universally applicable or missed some aspects of the tidal dynamics. Assimilation of sea level measurements by tide gauges and from space by radar satellites provided a solution to these problems.

In the last decade, a number of excellent parameterisations of the global ocean tide have become available. Some of these parameterisations are based purely on measurements from space (e.g. Figure 3), others are based on computer tide models that make use of only the known dynamics, and others are hybrid models that employ data assimilation. The two latter schemes provide information on tidal currents as well as tidal elevations. All three techniques are in agreement to within 1-2 cm which is a superb achievement. Proudman could never have dreamed of knowing the tide around the world so well, and it is thanks to him and others at Bidston leading the way that we now have an understanding of why the tide is so complicated.

Figure 3. Co-tidal chart of the M2 ocean tide: global map of lines joining places where high tides for M2 occur simultaneously, and places with equal tidal range. The lines indicate Greenwich phase lag every 30°, a lag of zero degrees being shown by the bold line, and the arrows showing the direction of propagation. The colours show amplitudes. Map provided by Richard Ray (Goddard Space Flight Center) for Pugh and Woodworth (2014).
Figure 3. Co-tidal chart of the M2 ocean tide: global map of lines joining places where high tides for M2 occur simultaneously, and places with equal tidal range. The lines indicate Greenwich phase lag every 30°, a lag of zero degrees being shown by the bold line, and the arrows showing the direction of propagation. The colours show amplitudes. Map provided by Richard Ray (Goddard Space Flight Center) for Pugh and Woodworth (2014).

The tide and surge models we have described above are usually operated in 2-dimensional mode (i.e. with the currents at each point in the grid taken as averages through the water column), and such model codes are relatively straightforward to construct and fast to run. A big change since the early days of the 1960s that first saw their construction is that modellers nowadays tend not to write their own codes, but instead adapt sophisticated modelling code packages written by others. This enables them to construct the 3-dimensional models of much greater complexity that are now used in research.

Numerical computer modellers now comprise one of the largest groups of scientists in oceanography laboratories such as the National Oceanography Centre in Liverpool (the successor of Bidston Observatory). Their models provide a way to make maximum use of oceanographic measurements from ships, satellites and robotic instruments in the ocean (and the ocean is a big place and there are never enough measurements) and a way to forecast how conditions in the ocean might evolve. It is inevitable that oceanography and many other aspects of science will rely on modelling more in the future.

 

Some References for More Information

  • Cartwright, D.E. 1999. Tides: a scientific history. Cambridge University Press: Cambridge. 292pp.
  • Heaps, N.S. 1967. Storm surges. In, Volume 5, Oceanography and Marine Biology: an Annual Review, edited by H.Barnes, Allen & Unwin, London, pp.11-47.
  • Murty, T. S., Flather, R. A. and Henry, R. F. 1986. The storm surge problem in the Bay of Bengal. Progress in Oceanography, 16, 195–233, doi:10.1016/0079-6611(86)90039-X.
  • Pugh, D.T. and Woodworth, P.L. 2014. Sea-level science: Understanding tides, surges, tsunamis and mean sea-level changes. Cambridge: Cambridge University Press. ISBN 9781107028197. 408pp.
  • Stammer, D. and 26 others. 2014. Accuracy assessment of global barotropic ocean tide models. Reviews of Geophysics, 52, 243-282, doi:10.1002/2014RG000450.
  • Wolf, J. and Flather, R.A. 2005. Modelling waves and surges during the 1953 storm. Philosophical Transactions of the Royal Society, A, 363, 1359–1375, doi:10.1098/rsta.2005.1572.

Tide Gauges and Bidston Observatory

Philip L. Woodworth, 4 August 2016.

Everyone knows that the level of the sea goes up and down. Most of these changes in level are due to the ocean tide (at Liverpool the level changes due to the tide by more than 8 metres at ‘spring tides’), but changes of several metres can also occur due to ‘storm surges’ that occur during bad weather, while slow changes in level can take place due to climate change and because of the geology of the adjacent land.

Changes in sea level are measured by devices called ‘tide gauges’: the more suitable name of ‘sea level recorders’ has never been widely adopted in the UK although Americans often call them ‘water level recorders’. There are as many types of tide gauge such as:

Vertical scales fixed to a jetty or dock entrance.

These were simple ‘rulers’ (sometimes called ‘tide poles’ or ‘tide boards’), by means of which the sea level could be measured by eye. An example is shown in Figure 1.

Figure 1. A simple ‘tide pole’ or ‘tide board’ installed vertically in the water by means of which the water level can be estimated by eye.
Figure 1. A simple ‘tide pole’ or ‘tide board’ installed vertically in the water by means of which the water level can be estimated by eye.
Float and stilling well gauges.

This way of measuring sea level was first proposed by Sir Robert Moray in the mid-17th century. However, over a century went by before the first practical systems were introduced at locations in the Thames during the 1830s. They quickly become the standard way of measuring sea level and by the end of the 19th century they had spread to major ports around the world.

A stilling well is a vertical tube with a hole at its base through which sea water can flow. The level inside will be, in principle, the same as that of the open sea outside, but energetic wave motion will be damped (or ‘stilled‘) inside due to the hole acting as a ‘mechanical filter’. In the well is a float which rises and falls with the water level, and is attached via a wire over pulleys to a chart recorder driven by an accurate clock. The rise and fall of the water level is thereby recorded as a line traced by a pen on paper charts that are regularly replaced, the charts finding their way to a laboratory such as that at Bidston Observatory, where an operator ‘digitises’ the pen trace and so provides the measurements of sea level.

Figure 2(a) demonstrates how the level of the float is recorded on the paper chart, while Figure 2(b) is a photograph of the tide gauge station at Holyhead where there are two exceptionally large stilling wells.

Figure 2a. An example of a float and stilling well tide gauge. In modern gauges of this type, the recording drum and the paper charts are replaced by digital shaft encoders and electronic data loggers.
Figure 2a. An example of a float and stilling well tide gauge. In modern gauges of this type, the recording drum and the paper charts are replaced by digital shaft encoders and electronic data loggers.
Figure 2b. Two large stilling wells at Holyhead in North Wales.
Figure 2b. Two large stilling wells at Holyhead in North Wales.

This type of gauge is of historical importance as they were used for almost two centuries (although with modern improvements such as replacing the paper charts with modern electronic data loggers) and so data from them make up the data sets of sea level change that are nowadays archived at the Permanent Service for Mean Sea Level (PSMSL) in Liverpool and used for studies into long-term climate change. During the 19th century, most of these gauges were operated in the UK by the major ports, and even by the railway companies which operated ferries. Bidston Observatory operated one at Alfred Dock in Birkenhead for many years. A number of countries still operate float and stilling well gauges although most in the UK have been replaced with other types.

Pressure gauges.

These gauges measure sea level by recording water pressure with the use of a pressure sensor that is installed well below the lowest likely level of the water. The recorded pressure will be the sum of two forces pressing on the sensor: the pressure due to the water above it (which will be the sea level times the water density and acceleration due to gravity) and the pressure of the atmosphere pressing down on the sea surface. In practice, the latter can be removed from the pressure measurement using what is called a ‘differential’ sensor, thereby, after some calculation, providing a measurement of the sea level.

We mention two types of pressure sensor below, which were both developed at Bidston. One type (the bubbler pressure gauge) has been used at 45 locations around the UK for several decades and remains the main technology for sea level measurements in this country. Until recently (mid-2016), this large network was operated for the Environment Agency by a group at Bidston called the Tide Gauge Inspectorate, and then, following relocation, at the National Oceanography Centre in Liverpool.

Ranging tide gauges.

These devices consist of a transducer that is installed over the sea so that it can transmit a pulse down to the water, where the pulse is reflected back and recorded by the transducer, so measuring the time taken to travel down and back. If one knows what the speed of the pulse is, then one can readily compute the height of the transducer above the sea, and so measure sea level. The transmitted pulse can be either an acoustic one (sound), or electromagnetic (radar) or optical (light). During the last decades of the 20th century, acoustic systems became very popular and replaced float gauges, and even replaced pressure gauges in some countries. However, they have since been largely replaced in their turn by radar gauges for several reasons. One simple reason is relative cost. However, radar gauges are potentially more accurate than acoustic systems owing to the speed of a radar pulse, unlike sound, being independent of air temperature. Optical ranging gauges use lasers to transit the pulses but, to my knowledge, are used in only two countries (Canada and South Korea).

Bidston Observatory had expertise in all of these types of tide gauge, but three can be mentioned in which Bidston scientists took a special lead.

Bubbler pressure gauges.

In the late 1970s, the Institute of Oceanographic Sciences (IOS, as Bidston Observatory was then known) was encouraged by the government to see if the new types of tide gauge then becoming available would be suitable for replacing the float and stilling well gauges then standard in the UK. This led to a programme of research by David Pugh and others into the use of different types of pressure gauge, including the bubbler gauge, and the curiously-named ‘non-bubbling bubbler gauge’ which we shall not explain.

Bubbler gauges were not invented at Bidston but they were developed there into practical instruments. They offered advantages over other pressure sensor systems in which the sensors themselves are installed in the water. In a bubbler system, the only equipment in the water is a tube through which gas flows at a rate sufficient to keep the tube free of water, such that the pressure in the tube is the same as that of the water head above the ‘pressure point’ at the end of the tube (Figure 3). The pressure sensor itself is located safely at the ‘dry land’ end of the tube, so there are no expensive electronic components that could be damaged in the water. If the tube is damaged it is simple and cheap to replace. The only drawback is that a diver is needed to install the tube, although the same need for a diver applies to all other pressure systems.

Figure 3. A outline of the bubbler pressure gauge system. (From Pugh and Woodworth, 2014).
Figure 3. A outline of the bubbler pressure gauge system. (From Pugh and Woodworth, 2014).

Comparisons of the old (float and stilling well) and new (bubbler) gauges were made at various locations, including at the important tide gauge station at Newlyn in Cornwall. In addition, the way that they measure sea level was thoroughly understood from both theoretical and experimental perspectives. The conclusion of the research was that bubbler pressure gauges could be reliably installed across the network. Bubblers are now standard in the UK and Ireland although they have since been replaced in countries such as the USA by other systems.

‘B’ gauges (where B stands for Bidston).

These gauges were developed in the 1990s by Bob Spencer, Peter Foden, Dave Smith, Ian Vassie and Phil Woodworth for the measurement of sea level at locations in the South Atlantic. They are rather complicated to explain in this short note, but the gist of the technique is that it uses three pressure sensors to measure sea water pressure (as in a bubbler gauge) and also maintain the datum (measurement stability) of the data in the record. ‘B gauges’ are probably the most accurate and stable types of tide gauge ever invented, but they are expensive (because of the requirement for three sensors) and were never developed commercially. Nevertheless, the principle of the ‘B technique’ was eventually incorporated into the way the bubblers were operated in the UK network, which remains the situation today.

Radar tide gauges.

Bidston Observatory cannot claim to have invented radar tide gauges; these radar transducers were developed first for the measurement of liquids and solids in giant industrial tanks, and were then applied to the measurement of river levels. However, Bidston can claim to have been one of the first laboratories to have used radar gauges for measuring sea level, a one year comparison of radar and bubbler data from Liverpool having shown that radar was a suitable technique for a tide gauge (Figure 4). Radar gauges have since fallen in price, are even more accurate than they were, can be readily interfaced to any kind of computer, and consume less power (an important feature in remote locations where gauges have to be powered from solar panels). They have become the standard technique for measuring sea level around the world and look like remaining so in the future.

Figure 4. A radar tide gauge at Gladstone Dock in Liverpool. The gold-coloured radar transducer transmits pulses down to the water and so measures sea level. The grey box on the wall is a satellite transmitter that sends the data to the laboratory.
Figure 4. A radar tide gauge at Gladstone Dock in Liverpool. The gold-coloured radar transducer transmits pulses down to the water and so measures sea level. The grey box on the wall is a satellite transmitter that sends the data to the laboratory.

Some References for More Information

  • Bradshaw, E., Woodworth, P.L., Hibbert, A., Bradley, L.J., Pugh, D.T., Fane, C. and Bingley, R.M. 2016. A century of sea level measurements at Newlyn, SW England. Marine Geodesy, 39(2), 115-140, doi:10.1080/01490419.2015.1121175.
  • IOC. 2015. Manual on Sea Level Measurement and Interpretation. Manuals and Guides 14. Intergovernmental Oceanographic Commission. Volumes I-V may be obtained from http://www.psmsl.org/train_and_info/training/manuals/.
  • Pugh, D.T. and Woodworth, P.L. 2014. Sea-level science: Understanding tides, surges, tsunamis and mean sea-level changes. Cambridge: Cambridge University Press. ISBN 9781107028197. 408pp.
  • Woodworth, P.L., Vassie, J.M., Spencer, R. and Smith, D.E. 1996. Precise datum control for pressure tide gauges. Marine Geodesy, 19(1), 1-20.

Hartnup moves in

This article appeared in the Liverpool Mercury on 20th December 1866, two days before Liverpool’s astronomer, John Hartnup, took possession of Liverpool’s shiny new observatory on Bidston Hill. It makes fascinating reading 150 years later.

The New Liverpool Observatory

Bidston-hill has hitherto been chiefly noted for its picnic parties, and for entertainments in which ham and eggs were the principal ingredients. It will now acquire a wider celebrity as the site of one of the most complete observatories at present in existence – one which is certain to make the Dock Board spoken of with respect by men of science, and to render Mr. Hartnup’s position, as astronomer of Liverpool, an object of something like envy to his professional brethren. For the interests both of the port and of science, it was certainly a good thing that the space which the old observatory has occupied during the last 22 years, on the Prince’s Pierhead, was required for docks. Close to the river on one side, and the murkiest part of the town on the other, Mr. Hartnup was often in a fog, not by any means intellectually, but materially, and still more frequently had his nicest observations interfered with by the smoky canopy which overhung his post of observation. Obliged to cast about for a new site, the dock board selected Bidston-hill as the most eligible situation to be found in the neighbourhood for an observatory. The design and erection of the building were left to Mr. Lyster, the dock engineer, and he and his staff have produced a work of which they have no reason to be ashamed. Commenced in 1864, it has been gradually growing up by the side of the old lighthouse, which formerly was the sole occupant of the height, and now with its two domes and picturesque outline, stands out as a prominent feature in the landscape. The transfer of instruments from the old observatory has been for some time in progress, and at the beginning of next year Mr. Hartnup will probably be able to resume his labours – made still more important by this change – under conditions more favourable than he has yet enjoyed.

Externally, the new observatory has a bold and massive appearance, which accords with the position in which it is placed. A building perched alone at the summit of a hill is in danger of looking insignificant from one or other points of view, but Mr. Lyster has so well arranged the different fronts that from all aspects an effective grouping is presented. Two domes, springing from octagonal towers at the east and west extremities of the south front, are prominent features of the building. Beneath one is the “equatorial”, for making astronomical observations, and beneath the other an instrument called the transit. The domes enclosing these instruments have apertures at several points, and are made to revolve, so that observations can be taken in any part of the heavens. The substantial character of the whole building strikes the observer at once. It is founded upon a rock, and if the waves as well as the winds could come to Bidston-hill, Mr. Hartnup’s castle would not be likely to fall. Strength and solidity are characteristics of Dock Board work, but there are special reasons for making an observatory, from foundation to summit, firm and secure as builders’ skill can contrive. Some of the operations carried on are so delicate that the variation of almost a hair’s breadth would seriously affect the results, and hence the utmost precautions have been taken to avoid the vibration to which all but the most substantial buildings are liable. A deep foundation excavated out of the solid rock and thick stone walls to form the superstructure were not considered sufficient to secure perfect immovability, and to prevent all possibility of vibration from anything short of an earthquake the building has been insulated from the surrounding rock to the depth of 12 or 14 feet by a trench about 18 inches wide. Even this has not been deemed a sufficently stable basis for the transit. That instrument is located immediately beneath the dome at the south-east angle of the building. It is used for taking the time, fixing the latitude, and determining the declination of the stars. These operations require the utmost accuracy of observation, and consequently the most perfect steadiness of position. To support the instrument a huge pillar, nine feet in diameter, has been carried up from the solid rock to the floor immediately beneath the dome, and this pillar, though passing through several floors, and apparently in contact with them, actually touches the building at no part. In other respects, the thorough adaptability of the building to the purpose for which it is intended has been studied. In many of the processes uniformity of temperature is very necessary, and towards securing this lofty cellars have been excavated in the basement, where an efficient heating apparatus, communicating with all the apartments in the building, is situated. The other internal arrangements are in a corresponding style of completeness. There is a fine chronometer room 36 feet long by 21 feet abroad; an anemometer room and a library, each 18 feet by 21 feet; a computation room; and, in short, every provision for carrying on efficiently the work belonging to an observatory. The northern portion of the building forms the private residence of Mr. Hartnup, and in reference to the arrangements of which it need only be said that the comfort and convenience of its occupant have been consulted in every particular.

There are a good many people in Liverpool, we dare say, who have a very shadowy notion of the objects of an observatory, and the labours which Mr. Hartnup has to perform. Quoting from his last report, we will let the astronomer tell in his own words what are the merely routine duties of the observatory :-

Observations are regularly taken with the transit instrument, for the purpose of ascertaining the local time. From the local time so obtained, the Greenwich mean time is deduced and communicated to the port daily by the dropping of the time-balls at the Observatory and at the Victoria Tower. The clocks at the Victoria Tower and Town Hall, and also the seconds clock seen from the Exchange flags, are controlled from the Observatory. The other public clocks on the dock estate are regulated twice each week, and a record is preserved showing their errors at the time they were regulated. The velocity and direction of the wind, and the fall of rain, as derived from the self-registering anemometer and rain-gauge, are tabulated for each hour of the day, and hourly readings are taken from the tracing produced by the self-registering barometer. The results thus obtained are tabulated, and the mean reading at each hour of the day is taken at the end of every month. The ordinary meteorological observations obtained by means of the standard barometer, thermometers, hygrometers, &c., are taken at eight and nine a.m., and at one, three, and nine p.m. daily. A telegram containing the corrected readings of the barometer, wet and dry thermometers, strength and direction of the wind, and general state of the weather for the proceeding 24 hours, is forwarded daily at eight a.m. to the Meteorological Department of the Board of Trade. Weekly meteorological observations are forwarded to the Mersey Docks and Harbour Board, and to the medical officers of health for Liverpool and Birkenhead. Monthly and weekly meteorological observations are forwarded to the Registrar-General of Births, Deaths and Marriages; and a tracing of the record produced by the self-registering barometer, together with an account of the hourly strength of the wind, &c., are supplied daily to the Liverpool Underwriters’ Association.

The value of the observatory in keeping an exact record of time is shown by the fact that in Liverpool there are, on an average, upwards of 2000 chronometers dependent on the time disseminated from the observatory for their errors on Greenwich mean time, and of their daily rates obtained while the ships to which they belong remain in port. Now that the observatory has been removed to Bidston, it is possible that the time-balls will give place to a time-gun, which is found to possess several advantages over the ball. With regard to meteorological observations, their importance is every year becoming more largely recognised, and during the last 20 years Mr. Hartnup has contributed not a little to the advance which this department of science has made by his carefully compiled tables of results.

In a more direct and immediate manner, the observatory at Bidston will be of immeasurable value to Liverpool by reason of the facilities it affords for testing nautical instruments. The seaman is chiefly dependent for a knowledge of his chronomoter, compass, sextant, &c. Errors in these have, times out of number, led to the destruction of noble ships, and the loss of many lives and the importance of efficiently testing nautical instruments has long been present to the mind of the astronomer. At the old observatory, chronometers only could be tested. Its nearness to the docks, the possible proximity of iron ships, and other disturbing influences, rendered the testing of compasses out of the question. At Bidston, all these difficulties will be removed, and it is proposed to erect a wooden house specially for the testing of compasses. If this be done, it is to be hoped nautical men will take advantage of the opportunity afforded them of ascertaining that their compasses act properly. It will also be possible at Bidston to test sextants; and if arrangements are made for that purpose, the Liverpool Observatory will be, with the single exception of Kew, the only place in the kingdom at which these instruments are tested. The practical advantage of subjecting instruments to a systematic test has already been exemplified in the case of chronometers. It is often that three or four voyages elapse before a captain ascertains the exact rate of his chronometer, whereas the testing process at the observatory puts him in possession of the information at once. This is the mode of testing chronometers –

All chronometers received at the Observatory are compared daily with the normal clock, which is kept as nearly as possible to Greenwich mean time. From subsequent astronomical observations, the daily errors of this clock, at the times of its comparison with the chronometer, are deduced, and the correction for each day, thus obtained, is applied to the daily comparisons of all the chronometers. In this way the error of each timekeeper is found daily, with as much accuracy as it is well possible to attain. The temperature in a glazed chamber is kept, by artifical means, between 50′ and 85′, and changed weekly 10′ or 15′, in order to show the change of rate that may be expected on going from a temperate to a tropical climate. The record supplied to the captain or owner of each chronometer, contains its error on Greenwich mean time for each of the first few days; and subsequently it is given at the end of each week, together with the mean daily rate, the temperature to which the instrument has been exposed, and the greatest variation of rate between any two days in each week. The corrections for imperfect adjustment are sometimes found to be so large or so irregular as to render it troublesome or difficult to apply them all efficiently, and in such cases the record becomes a serviceable guide to the maker, as it directs his attention to the peculiar fault, and often enables him to make the necessary adjustment at once.

It is rather puzzling to be told that the wind is made to register its own velocity, force, and direction; that the quantity of rain which falls is measured and recorded without human interference; and that the atmosphere marks its own variations on a sheet of paper. Yet all this is done by means of the anemometer, rain-gauge, and barograph – contrivances as ingenious as they are effective. Any one who has been in the neighbourhood of the observatory must have observed on the roof a sort of horizontal windmill, consisting of four hemispherical cups. These serve the double purpose of keeping a four-feet pressure plate facing the wind and turning the shaft which runs through into the room where the anemometer is situated. This shaft, by an ingenious contrivance, regulates the motions of a pencil placed in contact with a sheet of paper stretched round a slowly revolving cylinder. The sheets of paper which receive the record made by the pencil are divided by vertical lines into spaces equal to the hourly motion of the cylinder, and by horizontal lines into other spaces, representing the pressure of wind per square foot. The barograph, or self-registering barometer, has been in use about three years, and the Liverpool Observatory is the only institution which possesses an instrument of this character. It was invented by Mr. Alfred King, of this town, and shows great ingenuity of construction. In the ordinary barometer the variations in the atmospheric pressure are indicated by the varying height of a column of mercury within a tube; in the floating barometer these variations are made evident by the movements of the tube itself, and its changes of position are recorded in a somewhat similar manner to that adopted in connection with the anemometer. There are various other interesting features connected with the observatory, but we must bring this notice to a close. In many respects, the establishment of the new observatory is an important event, and there can be no question that Mr. Hartnup will turn to good account the increased advantages he will possess for carrying on his useful labours in the fine institution placed under his charge.