Tag Archives: lighthouse

Unknown Scottish Lighthouse

Can anyone identify the Scottish lighthouse in this drawing?

Drawing of unidentified Scottish Lighthouse

Drawing of unidentified Scottish Lighthouse

It was found in a box of plans in the Mersey Docks and Harbour Board collection at the Merseyside Maritime Museum Archives. The handwritten annotation reads “George F. Lyster Esq. with the compliments of D. &. T. Stevenson, Edin. 10 April 1871”.

David and Thomas Stevenson were brothers, sons of Scottish lighthouse engineer Robert Stevenson (who visited Wirral in 1801 and 1828). David and Thomas built many lighthouses together for the Northern Lighthouse Board.

In 1871, George Fosbery Lyster, Engineer-in-Chief for Mersey Docks, was planning a replacement for the old Bidston Lighthouse. Most likely, Lyster wrote to his counterparts in the NLB to request a copy of a drawing of a recent lighthouse of their design. We already know that he obtained drawings of St Bees Lighthouse from James Douglass of Trinity House at about the same time.

September is all about Scottish Lighthouses and the Stevenson dynasty. Yesterday, I wrote up Robert Stevenson’s remarks about the encroachment of the sea upon the Cheshire shore. Tomorrow, the NLB is opening their headquarters to the public. And at the end of the month, the Museum of Scottish Lighthouses is hosting the Annual General Meeting of the Association of Lighthouse Keepers.

Thanks to Yu-Chen Wang for bringing the drawing to my attention.

If you have any information that might help us identify this lighthouse, please comment on this post, or write to us via our contact page.

Women in the workplace

On International Women’s Day, we remember some of the important women in the history of Bidston Lighthouse and Observatory.

Elizabeth Wilding, Liverpool’s first female Lighthouse Keeper.

When Richard Wilding, keeper of Bidston Lighthouse, died in March 1797 at the ripe old age of 85, the Liverpool Dock Committee needed to appoint a successor. Richard’s widow, Elizabeth Wilding,  35 years his junior, had already been doing a lot of the work, so she was the natural choice but for one problem – she was a woman. Perhaps the Dock Committee were influenced by the fact that Mrs Cormes was doing a good job for the Chester trustees at Point of Ayr Lighthouse at Talacre, following her appointment as Lighthouse Keeper in 1791. Anyway, the Dock Committee did take the bold step of appointing Elizabeth in April 1797, albeit with some unusal conditions attached.

“Elizabeth Wilding Widow of the late Richard Wilding … is hereby appointed Keeper of the Bidston Lighthouse in Cheshire at the clear annual Salary of Fifty Pounds so long as she shall continue to behave herself properly and attentively and employ her Son in Law Captain William Urmson as her Assistant and shall not attempt to employ or use the said Building called the Bidston Lighthouse or any of its Appendages as a Publick House.”

Elizabeth died in service only three years later, and was succeeded by her son-in-law and assistant William Urmson, a former sea captain. She must have done a good job, because in later years the Dock Committee did not hesitate to appoint female keepers at other lighthouses – unlike Trinity House, who never appointed a woman as Principal Keeper in 500 years.

When John Jones was dismissed as keeper of Leasowe Lighthouse “for intoxication and insubordination” in 1854, his wife Ann was appointed as keeper in his place. Leasowe’s last lighthouse keeper was Mary Elizabeth Williams, who served from 1894 to 1908. And at Bidston, we had the Urmson sisters.

The Urmson sisters

William Urmson was assisted by his three daughers Ann, Jane and Catherine. This contemporary account by George Head in 1835 is delightful and illuminating.

Biddestone Hill, about three miles from Woodside, commands an extensive view of the country inland, while the forest of signal poles, with which the lighthouse is surrounded, give it, at a distance, an extraordinary appearance—that of a dock or harbour on the top of a hill. Hence the merchant vessels bound to Liverpool are signalled and telegraphed in the offing, the poles alluded to bearing the private signals of different individuals. And what must be remarked as rather singular is, that, notwithstanding the arduous duty which necessarily falls on the station, the whole is performed, almost exclusively, by young women, daughters of the veteran in charge. The old man, who is thus ably supported in the winter of life, is fourscore years old, and has held the office upward of forty years. Although boys are employed to run backward and forward, out of doors, with colours to the poles, and haul them up; and one of the three young women is married, and occasionally assisted by her husband; yet it is she who, being perfect in the whole code of signals, performs the responsible part of the duty. This couple were both at work together at the time I arrived, the young woman keeping the lookout, and calling the numbers, while the man, merely at her bidding, pulled the ropes. She not only kept him employed, but managed meanwhile to iron a shirt into the bargain.

The business of the youngest sister is to attend the light, consisting of eleven Argand lamps, with plated reflectors. Every four hours during the night the lamps are trimmed; these, the stove, copper, oil jars, and paved floor, are preserved in a state of cleanliness not to be exceeded; while no doubt, many a mariner, on a wintry and stormy night, both knows and feels that his life and safety are thus well confided to the never-failing care of — woman.

The old man in the story is William Urmson, who died later that very year. The three women were the surviving daughters of his second wife:  Ann (who was to succeed William as keeper), Catherine (the youngest, who attended the light), and Jane (who kept the lookout and called the numbers).

In their turn, Ann and Jane respectively held the offices of lighthouse and telegraph keeper in their own right. But you would glean a very different impression from the census records, which list Ann only as the wife of John Urmson, Lighthouse Keeper and Jane as the wife of Thomas Nichols, Telegraph Keeper. Urmson was both Ann’s maiden and married name; her husband John was a second cousin.

Doodson’s “Computers”

Arthur Doodson, the man behind the mechanical tide predicting machines at Bidston Observatory, exclusively employed young women to operate them. Their job title was “computer” and an essential qualification for the post was good handwriting. These young ladies computed tide tables around the world, including those that were used to plan the D-Day landings.

The ladies in this post-war photograph of the Observatory Staff by the One O’Clock gun are, proceeding clockwise from Valerie Doodson at the front left:
Valerie Doodson née Boyes, Jean Harman née MacFarlane, Dorothy Ainsworth, Eunice Murrell née Heath, Barbara Trueman-Jones, Margaret Lennon née Weston, Sylvia Asquith née Brooks, Margaret Ireland née Wylie, and Olwyn Branscombe.

Observatory staff by the one-o-clock gun

Observatory staff by the one-o-clock gun.

Mary Connell

For seventy-seven years, Mary Connell was a constant presence on the hill that she loved. She moved into the Lighthouse Cottages in 1937 with her parents Mick and Mary Connell and younger sister Patricia. She worked as a funeral director for many years, and walked her dogs on Bidston Hill twice a day. She fought the combined lawyers of Wirral Borough Council and the Natural Environment Research Council for the right to stay in the Lighthouse Cottages, and against all the odds, she won. She was in her seventies when ill health forced her to retire.

After the Proudman Oceanographic Laboratory abandoned Bidston Hill in 2004, Mary was the only person living on the site (until guardians were eventually installed in the Joseph Proudman Building and the Observatory). Her only defenses against the disaffected youths who prowled the site at night were a walking stick, her sharp tongue, and the brambles she allowed to grow around the Lighthouse Cottages. Her sharp tongue was the most formidable of these. We miss her.

Mary Connell, 1934-2014

Related articles

The world’s most inland lighthouse

Bidston Lighthouse is the world’s most inland lighthouse.

By this I mean that of all the lighthouses in the world that were constructed as genuine navigational aids to mariners, none were built further from the body of water they lit than Bidston’s.

Liverpool’s Sea Lights were a pair of leading lights that guided ships through the Horse Channel.  A line drawn from the upper light at Bidston through the lower light at Leasowe crosses the high water mark on Mockbeggar Wharf at a distance of 2.1 nautical miles (2.4 statute miles, or 3.9 kilometres). The distance between the upper and lower lights is 2 nautical miles (2.3 statute miles or 3.7 kilometres), also making the Sea Lights the furthest apart of any pair of leading lights in the world.

There are, of course, many lighthouses further from the sea than Bidston’s. They can be found on river banks, or canals, or lake shores, and have provided valuable service to mariners as navigational aids. But these were all built relatively close to the body of water that they lit.

I also rule out aerial lighthouses, such as the one at RAF Cranwell, in Lincolnshire. A few of these were built as navigational aids to pilots, not mariners, and they lit the sky, not the sea.

Some otherwise interesting “lighthouses” are disqualified on the grounds of not being genuine navigational aids to mariners.

During  the 1920s, Benito Mussolini ordered the construction of a lighthouse atop his summer palace at Rocca delle Caminate, some 25 kilometres from the Adriatic Sea, and commanded the Italian Navy to include it in their list of operational lights. Flashing red, white and blue when Il Duco was in residence, it provided good service as a monument to the dictator’s vanity. Perhaps it helped the locals find their way home in the dark, but it was of no use to mariners as a navigational aid.

Rocca delle Caminate in 1939. Photo by E. Zoli Forlì.

Rocca delle Caminate in 1939. Photo by E. Zoli Forlì.

Cape Todd Lighthouse stands in the desert of central Australia, near Alice Springs, on the banks of the Todd River, which is usually dry. That doesn’t stop the Aussies from holding the annual  Henley-on-Todd regatta, in which contestants bring their own bottomless boats and carry them at a run along the Todd River. They like to claim that the Lighthouse is a navigational aid, because it stops the contestants from running out of bounds during the race. Built by amateur radio enthusiasts, Cape Todd Lighthouse took part in the International Lighthouse and Lightship Weekend in 2013 and again in 2014, when it was listed as a “faux” lighthouse.

Cape Todd Lighthouse, near Alice Springs, Australia

Cape Todd Lighthouse, near Alice Springs, Australia

I stand by my claim until such time as someone provides evidence of a greater distance, or the Italian Navy blockades Liverpool in protest.

If you do know of any interesting inland lighthouses, please let us know by commenting on this post. We’d also like to hear about any claims for the most inland operational lighthouse, or for the most widely separated operational pairs of leading lights.

Further reading

 

Female Lighthouse Keepers

Lighthouse keeping is generally regarded as a male profession. But it was not uncommon for a lighthouse keeper to be assisted by his family, and no doubt many seafarers owe their lives to the wives and daughters who kept the light burning when the keeper was ill, asleep or in his cups.  Most of these women have been forgotten by history, with the notable exception of Grace Darling.

Lucy, the keeper in Margaret Elphinstone’s well-researched and insightful novel “Light“, is fictional.

Trinity House, which celebrated its 500th anniversary in 2014, never appointed a woman to the post of Principal Keeper (PK). It probably never will, because the UK’s last manned lighthouse, North Foreland, was automated in 1998.

Liverpool’s Dock Committee was more enlightened. They appointed Elizabeth Wilding as keeper of Bidston Lighthouse in 1797 (albeit with conditions attached), following the death of her husband Richard. She was succeeded by her son-in-law and assistant William Urmson in 1800. Ann Urmson, William’s second daughter by his second wife,  was PK at Bidston from 1835 until 12 May 1869. Richard, Elizabeth, William and Ann all died in service. William’s other daughters helped at the Bidston station: Jane kept the telegraph, and Catherine assisted at the lighthouse.

Leasowe Lighthouse also had two female Principal Keepers. When John Jones was dismissed “for intoxication and insubordination” in 1854, his wife Ann was appointed in his place. John died in 1857, still a resident of the lighthouse. Ann Jones died in service on 23 Jul 1867. [1, pages 33-34]. The last lighthouse keeper at Leasowe Lighthouse was Mary Elizabeth Williams. When her husband Thomas Williams died in 1894, Mrs Williams took over as PK. Apart from the lighthouse, she also had eight children (including a baby) to look after. Fortunately, some of her children were old enough to help. She was still in post when Leasowe’s light was discontinued on 15 July 1908. After the closure, she carried on as caretaker until November of the following year [1, pages 37-40].

Elizabeth Wilding was the first female lighthouse keeper to be appointed by Liverpool. But the Chester trustees were a few years ahead, having appointed Mrs Cormes as keeper of Point of Ayr Lighthouse in 1791 [1, page 46].

In 1975, the Lancaster Port Commission appointed Peggy Braithwaite née Swarbrick (9 Jul 1919 – 12 Jan 1996) as Principal Keeper of Walney Island Lighthouse, when her husband, the lighthouse keeper, died. Peggy retired at the age of 74.

If you know of any women who served as Principal Keeper, please let us know by commenting on this post.

References

  1. John and Diane Robinson, Lighthouses of Liverpool Bay, Tempus Publishing Ltd, 2011.

Drawing of unknown lighthouse, 1871

Can anyone identify the lighthouse in this drawing?

Drawing showing plan and elevations of unknown lighthouse, possibly by James N. Douglass, 1871.

Plan and elevations of unknown lighthouse, possibly by James N. Douglass, 1871.

The drawing was found in a box containing plans of Bidston Lighthouse in the Mersey Docks and Harbour Board collection at the Merseyside Maritime Museum Archives. It is signed and dated Jas. N. Douglass, 1871 (I think). If my reading of the signature is correct, then the architect would be the famous James Nicholas Douglass F.R.S., who built many important lighthouses for Trinity House, including the fourth Eddystone Lighthouse.

Was this design commissioned by Mersey Docks for the new Bidston Lighthouse only to be rejected in favour of a later design by the MDHB’s own George Fosbery Lyster? Or was it for another lighthouse altogether, perhaps used as inspiration for Lyster’s own design?

If you have any information that might help us identify this lighthouse, please comment on this post, or write to us via our contact page.

ALK AGM 2015

The Annual General Meeting of the Association of Lighthouse Keepers took place on the Island of Portland, in Dorset, on the last weekend in September, 2015. There were excursions to Anvil Point Lighthouse, Portland Bill, the old Portland upper and lower lights, and a boat trip out to the Portland Breakwater Light. Anvil Point and Portland Bill are still operational. The old upper light is now holiday accommodation, and the lower light is a bird observatory. It was a privilege to visit the breakwater light with retired lighthouse keeper Gordon Medlicott, who was stationed there in 1967, the year it was decommissioned.

The French Visitor

In 1785, the French engineer Joseph Cachin drew this delightful illustration of Bidston Lighthouse.

Drawings of Bidston Lighthouse and reflector, by Joseph Cachin, 1785.

Drawings of Bidston Lighthouse and reflector, by Joseph Cachin, 1785.

Cachin’s careful drawings include a scale, and one can take measurements from them. The scale is in toises and pieds du roi. These units were used in France before the Revolution. There were twelve pouces in one pied du roi, and six pieds du roi in one toise. Pouce, pied du roi and toise correspond respectively to the Imperial units inch, foot and fathom, but were slightly longer. Thus one toise was 1.066 fathoms, 6.394 feet, or 1.949 metres.

If you measure the diameter of the reflector in the drawing using Cachin’s scale, and convert back to Imperial units, you should get a value very close to 12 feet. This is the size that William Hutchinson reported in 1777 in his Treatise on Practical Seamanship, but less than the thirteen-and-a-half feet reported by Robert Stevenson when he visited Bidston Lighthouse in 1801. Perhaps Stevenson was more casual while he was still learning the trade of lighthouse-engineering, for he seems also to have exaggerated the height of Leasowe Lighthouse.

Bidston’s reflector was (probably) the largest parabolic reflector ever to be installed in an operational lighthouse. It was also one of the first – Hutchinson installed parabolic reflectors in all the Wirral lighthouses about the same time. Hutchinson’s breakthrough in lighthouse optics was driven by the needs of Bidston Lighthouse, which was built further from the body of water it lit than any other lighthouse in the world (a record it holds to this day).

As far as I know, Cachin’s is the only drawing to show a cross section of the lamp room, with the stairs that the keeper would climb to replenish the oil reservoir, and the elaborate chimney through which the smoke and vapours of the lamp would escape.

Joseph Cachin (1757-1825) was a French engineer, best known for his work at Cherbourg Harbour. In 1785, while at the École Nationale des Ponts et Chaussées, he travelled to Britain and the United States. In England, he visited the ports of Sheerness, Liverpool, Bristol, Portsmouth, the quarries of Portland, and the Hospital at Greenwich. He examined lighthouses and lime-kilns, the cranes on the Bridgewater Canal, and studied the materials used in their construction. (Readers of French can check my translation against this article.)

My thanks to Thomas Tag of the United States Lighthouse Society for bringing the drawing to my attention.

Has anyone seen our lamp?

This is a photograph of the lens that was installed at Bidston Lighthouse in 1873.

1st order dioptric lens with vertical condensing prisms, made for Bidston Lighthouse

1st order dioptric lens with vertical condensing prisms, made for Bidston Lighthouse

It was a first order dioptric lens with vertical condensing prisms, manufactured by Chance Brothers of Birmingham. The photograph was taken in the factory, before the lens was dis-assembled, shipped to Bidston Hill, and re-assembled in the lamp room of Bidston Lighthouse.

It shone every night for forty years, until it was finally switched off on 9th October, 1913, at sunrise.

We don’t know what happened to it after that. Did it sit, forgotten and ignored, in Bidston Lighthouse for many years? Was it transferred to a museum? Or was it re-deployed in another lighthouse?

National Museums Liverpool don’t have it (but they do have a smaller one that was used at Hale Head Lighthouse).

Given that it was a very expensive piece of equipment, originally costing much more than the tower that housed it, it would have made sense to re-deploy it another operational lighthouse.

Have you seen our lamp?

Update

In the Mersey Docks and Harbour Board collection at the Merseyside Maritime Museum’s Archives, there is a “worked up paper” on lighthouses.  It contains a memorandum for October 1913, stating that the Board agreed to a suggestion from the Marine Surveyor “that the lighting apparatus at the Bidston Lighthouse be fixed in the North Wall Lighthouse in substitution for the present one”. The North Wall Lighthouse, also known as the Bootle Lighthouse (or Bootle Bull) was built in 1877 at the north end of Liverpool’s Dock system, and discontinued in 1927 to make way for Gladstone Dock.

Drawing of North Wall Lighthouse in 1927

North Wall Lighthouse in 1927, from “Sea Breezes”, December 1973

The minutes of the Marine Committee of the Mersey Docks and Harbour Board for 21 Nov 1927 state that “The Account Sales in respect of Glass Prism Panels &c from the North Wall Lighthouse were submitted”. Unfortunately, the minutes do not record who bought the prisms, nor how much was paid.

Our quest continues.

Acknowledgments

My thanks to Thomas Tag for bringing the photograph to my attention, and to the helpful staff at the Merseyside Maritime Museum’s Archives.

Bidston Lighthouse used to prove Earth flat

In the nineteenth century, a fellow called Samuel Birley Rowbotham promoted a flat earth system which he called Zetetic Astronomy. Writing under the pseudonym “Parallax”, Rowbotham published Zetetic Astronomy: Earth Not a Globe in 1865. He drew on, amongst other things, information published in Lighthouses of the World by Alexander G. Findlay (1861-2) to support his thesis that the earth was flat. Bidston Lighthouse was one of his chief examples:

By the same authority, at page 39, the Bidston Hill Lighthouse, near Liverpool, is 228 feet above high water, one bright fixed light, visible 23 nautical or very nearly 27 statute miles. Deducting 4 miles for the height of the observer, squaring the remaining 23 miles and multiplying that product by 8 inches we have a downward curvature of 352 feet; from this deduct the altitude of the light, 228 feet, and there remains 124 feet as the distance which the light should be below the horizon!

Over a hundred years later, Robert J. Schadewald picked up the story in his 1992 article Looking for Lighthouses. Schadewald, like the Reverend M. R. Bresher before him, vigorously refuted Rowbotham’s arguments, but could not explain the anomalies in Lighthouses of the World. Schadewald concluded:

And what about Rowbotham’s anomalous lighthouses? Beats me. Perhaps the reported observations were made under unusual conditions. Perhaps, for those lighthouses still operating, new observations would not confirm the reported anomalies. By now, however, some of Rowbotham’s lighthouses presumably have been closed, torn down, or destroyed by the elements. For these, we will never know. One thing is certain; those who seek only anomalous lighthouses will never find light.

My inner geek can’t leave it at that. You can bear with me as I try to make sense of it, or you can read this instead.

I should disclose at this point that I do not, and never have, subscribed to any Flat Earth theory.

Elevation of the lamp

Let’s start with Findlay’s Lighthouses of the World. The entry for Bidston is on page 39.

Entry for Bidston in Lighthouses of the World,1861

Figure 1. Extract from “Lighthouses of the World”, Alexander G. Findlay, 1861.

Findlay explains the meaning of each column on page 32. Bidston is written in block capitals because it is a principal light. The black circle in column 4 denotes a catoptric reflector. To avoid any ambiguity, I quote Findlay’s explanations of columns 5 and 6 verbatim:

Height above high water (5th column). This gives the height of the flame above the highest tide level, consequently it is its minimum height, and is increased by the tidal range of the place. The height of the lighthouse itself, from base to summit, is given sometimes in the third column.

Visible in miles – sixth column. This gives the minimum distance to which the light can be seen, in clear weather, from a height of 10 feet above the sea level. But in the case of the principal lights this but imperfectly represents their range, as they could be seen at any distance attainable by increased elevation. In the use of coloured lights this range is given according to their presumed power.

The range is given in nautical miles. 23 nautical miles is 26.5 international miles or 42.6 kilometres, near enough.

The elevation is the height of the flame, and is given as 228 feet above high water. This is difficult to check, as the original Bidston Lighthouse was replaced in 1873. The new lighthouse was built a few yards or so to the north of the original, and there was extensive work on the foundations. So the elevations at the bases of the 1771 and 1873 towers could have differed by  a metre or two. And while some contemporary descriptions give a height for the tower (e.g. 55 ft according to Burdett’s Chart of 1771 [Rees 1949]), it is not clear whether these include the weather vane, chimney or flagpole erected atop the tower.

As Bidston Lighthouse is some two miles from the sea, the location of the high water mark to which the elevation is referenced is not immediately obvious. There are two reasonable choices. One is at the north coast of the Wirral peninsula, somewhere along Mockbeggar Wharf. The other, more likely, is Liverpool docks. Bidston Lighthouse was visible from both. There are good reasons to assume that the elevation was referenced to Liverpool docks. Ever since William Hutchinson started his tidal measurements in 1764, the tides at Liverpool were the most carefully observed in the British empire. It is no accident that Liverpool was the national reference point for elevation (Ordnance Datum). The original Liverpool levelling was started in 1840 using a bench mark on St John’s Church. In 1844 the datum was changed to the tidal pole in Victoria Dock. It was not until 1921 that the Ordnance Datum was changed to Newlyn, Cornwall. Given all this, it is reasonable to assume that the elevation of the Bidston light was known as precisely as any other in the country.

We can at least check whether Findlay’s reported 228 feet is plausible. We know that the elevation (relative to mean sea level Newlyn) of the base of the present Lighthouse is 59 metres (193 feet). The correction from Ordnance Datum Newlyn to Ordnance Datum Liverpool is negligible (only 0.1 feet at Ordnance Survey grid reference SJ 2889).

Let us take Findlay’s 68 feet for the height of the tower at face value. Doing the sums, we find the elevation of summit of the tower was 260.5 feet (79.4 metres), relative to mean sea level.

But Findlay gave his elevations relative to high water, not mean sea level. Now, the tidal range at Liverpool is the second highest in the country, nearly 10 metres at spring tides. (At neap tides, the range is about 4 metres). To convert to elevation above high water, we need to subtract about 5 metres, being half the maximum tidal range. So, the top of the tower was about 244 feet (75.4 metres) above high water, some 16 feet above the 228 feet that Findlay reports for the elevation of the flame. You can judge for yourself whether the following contemporary illustrations are consistent with the summit of the tower being 16 feet above the centre of the lamp room.

Bidston Lighthouse by Robert Salmon, Oil on Canvas, 1825. Courtesy of National Museums Liverpool.

Figure 2. Bidston Lighthouse by Robert Salmon, Oil on Canvas, 1825. Courtesy of National Museums Liverpool.

Bidston Lighthouse, from "Sailing Directions from Point Lynas to Liverpool", 1840.

Figure 3. Bidston Lighthouse, from “Sailing Directions from Point Lynas to Liverpool”, 1840.

Are there any other contemporary descriptions of Bidston Lighthouse?

Graham Hill’s “Navigation of the Irish Sea” (1851) agrees with Findlay in terms of both elevation, and range.

Extract from “The Navigation of the Irish Sea”, Graham H. Hills, 1851.

Figure 4. Extract from “The Navigation of the Irish Sea”, Graham H. Hills, 1851.

However, Henry Mangles Denham F.R.S., who personally surveyed Liverpool Bay, gives a different account in his “Sailing Directions from Point Lynas to Liverpool”, 1840.

Extract from "Sailing Directions from Point Lynas to Liverpool", 1840

Figure 5. Extract from “Sailing Directions from Point Lynas to Liverpool”, Henry Mangles Denham, 1840.

Denham’s quoted elevation of 244 feet is referenced to half-tide level. Subtracting 5 metres to make it relative to high water, we get 227.6 feet.

So all three contemporary sources (Findlay, Hills and Denham) agree on the elevation of the lamp to within a foot, i.e. 228 feet above high water. As I’m in no position to argue, I shall adopt this figure henceforth.

Range of the light

Knowing the elevation of the lamp, it should be just a simple matter of geometry to work out at what distance the light will disappear below the horizon for a ship-board observer. There are some complications of course: sea levels rise and fall and the tides around Liverpool are unusually high;  the earth is better described as an oblate spheroid than a sphere; and the path of light near the earth’s surface bends because of atmospheric refraction. Refraction is the most difficult to deal with, because the magnitude of the effect depends on prevailing weather conditions, notably the amount of moisture in the air and how this varies along the path from the light to the observer. For more information, see Andrew T. Young’s comprehensive article “Distance to the Horizon“.

In the following chart, I have plotted the range of a light (in nautical miles) as a function of its elevation (in feet).  The red curve shows the range to the horizon, ignoring atmospheric refraction. The green curve shows the range of the light for a shipboard observer 10 ft above the water line, again ignoring atmospheric refraction. The blue curve is the same as the red curve, but corrected for atmospheric refraction; I have used the “standard” correction of 8%, although in reality the effect can be significantly more or less, depending on prevailing conditions. The purple curve is the same as the green curve, with the same 8% correction for atmospheric refraction. I have drawn vertical lines at 10 ft (the standard elevation of a shipboard observer as adopted by Findlay), 228 ft (the elevation of the Bidston Light relative to high water), and 260 feet (the elevation of the Bidston Light relative to low water).

Plots of lighthouse visibility as a function of the elevation of the light.

Figure 6. Theoretical lighthouse visibility as a function of the elevation of the light. (1) Distance to horizon from the light (red). (2) Range of light for a shipboard observer at 10 ft above the water line (green). (3) As (1), with “standard” 8% correction for atmospheric refraction (blue). (4) as (2), corrected for atmospheric refraction (purple).

Thus the theoretical visibility of the Bidston Light for a shipboard observer at 10 ft above the waterline at high water matches Denham’s reported range of 21 nautical miles exactly, provided that we make an 8% allowance for atmospheric refraction.

I venture to say that Findlay’s quoted range of 23 nautical miles was actually wrong, at least by his own criteria.

But when you think about it, the conditions required to measure Findlay’s ranges would not have been that easy to arrange. At the moment when the light first came into view, the observer had to be 10 feet above the waterline, at high water, in clear weather, and have an independent measure of the distance to the light.  Other factors made matters even more difficult. A ship’s waterline depends on how heavily laden it is. Waves could increase the effective height of the observer. And because it takes a certain amount of time for the tide to come in (the difference in time between high tides at Holyhead and Liverpool is about 40 minutes), the mutual horizon of the observer and the light (i.e. the point where a light ray from the lamp to the observer grazes the sea) would sometimes be slightly lower than the observer’s waterline.

The range is much more sensitive to the elevation of the observer than to the elevation of the light itself. Adding seven feet to the elevation of the observer increases the range by more than one nautical mile.

On the other hand, adding seven feet to the elevation of the light increases the range by just under a quarter of a nautical mile. This places a limit on the correction one could make for the sheer size of Bidston’s reflector. The original reflector of 1771 was 12 feet in diameter (according to William Hutchinson, or 13-and-a-half feet according to Robert Stevenson) so the top of the reflector would have been above the horizon when the centre was still below it. We do know that by 1835, Bidston’s single reflector had been replaced by eleven smaller ones, but we don’t know their configuration.

Given all this, and taking variations into atmospheric refraction into account, the Bidston Light might well have been seen at 23 nautical miles, or even farther, under extreme conditions such as looming. And given the pride that Liverpool had in its principal light, for Liverpool to report anything less to Findlay would have been unthinkable.

Conclusions

The range of 23 nautical miles that Alexander G. Findlay quoted for the Bidston light in his Lighthouses of the World was not correct. By Findlay’s own guidelines, it should have been the minimum range in clear weather for a shipboard observer, 10 feet above the waterline, at high water.

Henry Mangles Denham got it right when he reported a range of 21 nautical miles in his Sailing Directions from Point Lynas to Liverpool.

However, the Bidston light would sometimes have been visible at Findlay’s quoted range, or even further, and it is easy to forgive Alexander George Findlay.

But one thing is certain: the data in Lighthouses of the World was not fit for Samual Birley Rowbotham’s purpose. He abused it terribly. This is harder to forgive.

References

  • Robert J. Schadewald, Looking for Lighthouses, 1992.
  • Zetetic Astronomy: Earth Not a Globe, Samuel Birley Rowbotham writing under the pseudonym Parallax, 1865.
  • A description and list of the lighthouses of the world, Alexander George Findlay, 1861. Available as an e-book from Google Play.
  • Navigation of the Irish Sea, Graham Hills, 1851.
  • Sailing Directions from Point Lynas to Liverpool, Henry Mangles Denham, 1840.
  • History of the Liverpool Pilotage Service, Mentioning the Local Lighthouses and Lightships, by John S. Rees, Southport Guardian, 1949.
  • Wikipedia article Horizon, retrieved 3 Nov 2014.
  • Andrew T. Young, Distance to the Horizon, retrieved 3 Nov 2014.

Afterword

Rowbotham went on to revise and expand his “Zetetic Astronomy: Earth Not a Globe”. The text of the 1881 edition is available on-line. In the 1881 edition, there is only one mention of Bidston Lighthouse, on page 27. He writes:

From the lighthouse on Bidstone Hill, near Liverpool, the whole length of the Isle of Man, on a clear day and with a good telescope, is distinctly visible, and presents the same horizontal base line as that observed in the Isle of Wight.

Now, I have stood in the lamp room of the present Bidston Lighthouse (which was built in 1873, eight years before the 1881 edition of Zetetic Astronomy) many a time, and I have yet to see the Isle of Man. Even the peak of Snaefell is beneath the horizon under normal conditions.

Perhaps Rowbotham’s sightings of the Isle of Man occurred atop the original lighthouse? Although the elevation of the Bidston Light was little changed when the present lighthouse was built, the original lighthouse did have the advantage of a viewing gallery above the lamp room, if Salmon’s painting is to be trusted (see Figure 1).  This should not have been enough to bring the entirety of the Isle of Man into view, but perhaps sightings of Snaefell from the original Bidston Lighthouse were less exceptional than today.