Tag Archives: BidstonLighthouse

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.

Not for sale

Bidston Lighthouse is not for sale, contrary to reports in the Sun today (Wednesday 20 August, 2014).

The Sun ran a short article about publicly owned property up for sale and gave it pride of place on page 2 (adjacent to the midriff of the page 3 girl). Sun readers were informed that:

Also up for auction is an airfield, and the Bidston Observatory, Merseyside, which comes with a laboratory and lighthouse.

The Sun has managed to squeeze three factual errors into a single sentence.

The Grade-II listed Bidston Observatory is for sale, but not by auction. It has been on and off the market for ten years. Whoever buys it will be taking on a massive responsibility. A buyer who accepts the moral duty to preserve this important piece of Merseyside heritage and finds a way to open it to the public will be able to count on considerable community support, and ours. Conversely, a buyer otherwise inclined should expect opposition at every turn.

The laboratory would be the Joseph Proudman Building, which was demolished in February 2013. Neither the freehold nor the leasehold of the vacant site, which was originally the kitchen gardens for the lighthouse, is currently on the market.

The lighthouse is privately owned. We are not selling. But visitors are welcome on open days and other special occasions. We still have a few places left on tours we’re running for next month’s Wirral Heritage Open Days.

Ironically, Bidston Observatory is publicly owned but is not open to the public at all.

In defence of the Sun, they are not the first to confuse the Observatory and Lighthouse. This postcard, based on an 1830 engraving of the old Bidston Lighthouse and Signals Station has the caption “Bidston Hill Observatory 1830”. The Observatory was not built until 1866, when it replaced the original Liverpool Observatory which was forced to relocate due to the expansion of Waterloo Dock.

Postcard-NotBidstonHillObservatory1830.jpg

 

 

Bidston Signals

Bidston Signals - early illustration

Bidston Signals – early illustration

This delightful illustration of the Bidston Signals was reproduced in “Romance of the Modern Liner”, by Captain E.G. Diggle, 1930. My thanks to Geoff Topp for bringing it to my attention.

Can anyone help with more information about the provenance of the original? Who painted it and when? If so, please comment on this post.

Gipsey in Three Positions Off Egremont

"Gipsey in Three Positions Off Egremont", Miles Walters, oil on canvas, c. 1828. Image courtesy Vallejo Maritime Gallery, Newport Beach, California.

“Gipsey in Three Positions Off Egremont”, Miles Walters, oil on canvas, c. 1828. Image (c) Vallejo Maritime Gallery, Newport Beach, California.

Miles Walters (1773-1849) was born in Ilfracombe, Devon. In his own words “The Artist in his Youthful Days worked in a Mold Loft and has been 13 years at Sea and has painted upwards of 200 Ships in the last Six Years and Sent them to all corners of the World.” He moved to Liverpool some time during the 1820s. Overshadowed by his more famous son Samuel Walters, Miles’ work is characterised by an exceptional attention to detail. His experience as a shipwright and seaman comes through in every line, flag and pennant, and the landmarks in the background of his paintings.

In this painting, the observer is looking across the mouth of the Mersey from Liverpool towards the Wirral peninsula. The ship Gipsey, the subject of the painting, is shown in three different positions. You can just make out Fort Perch Rock in the background, near the base of the rear mast in the central view of the Gipsey. Gipsey was built in 1826, and construction of Fort Perch Rock started in the same year and finished about 1829.

The artist has also taken pains to show Bidston Lighthouse and some of the signal poles that ran the length of Bidston Hill. You can see them clearly in this higher-resolution detail of the extreme left of the painting.

Detail showing Bidston Signals.

Detail of “Gipsey in Three Positions Off Egremont”, showing Bidston Lighthouse and Signals. Miles Walters, c. 1828. Image (c) Vallejo Maritime Gallery.

I am grateful to Vallejo Maritime Gallery for permission to use these images, and to Colin Dilnot for bringing this wonderful painting to my attention.

Further reading

  • “Marine Art & Liverpool: Painters, Places & Flag Codes 1760-1960″, A. S. Davidson, Waine Research Publications, 1986, ISBN 0 905184 10 6.

Lines of Sight

The history of Bidston Hill is all about line of sight communications. From Bidston Hill, one can see (and be seen) for many miles in all directions.

Fire Beacons have been deployed on Bidston Hill for centuries. We know they were prepared as part of an early-warning system during the Spanish Armada and again during the Napoleonic Wars. They may have been used even earlier.

In navigation, the Windmill on Bidston Hill was used as a “day mark” long before Wirral’s first lighthouses were built in 1763. This is why many early sea charts of Liverpool Bay took pains to mark the location of Bidston Windmill.

The Bidston Signals comprised more than a hundred “lofty flagstaffs” running along the ridge of Bidston Hill. Their purpose was to give the port of Liverpool notice of arriving ships.

Bidstone Lighthouse and Signal

Bidstone Lighthouse and Signals, by Henry F. James, c. 1807. The original is in the collection of the Williamson Art Gallery.

Lighthouses, too, depend on line of sight. To be useful, they must be seen. Liverpool’s first lighthouses were built in Wirral in 1763. These were navigational aids, not warning lights. By setting a course with the two lights straight ahead, mariners avoided the treacherous sand banks of Liverpool Bay. The two Sea Lights, near Leasowe, marked the safe passage through the Horse Channel, and the two Lake Lights marked the way into Hoyle Lake. This was an early (but not the earliest) use of leading lights in navigation.

The first Bidston Lighthouse was built in 1771, near the Signals Station. It was needed because the lower Sea Light had been overwhelmed by storms. Bidston Lighthouse became the upper Sea Light, and Leasowe Lighthouse, still standing today, became the lower Sea Light. Being 2.3 miles further inland, the new lighthouse depended on a breakthrough in lighthouse optics, which came in the form of William Hutchinson’s invention of the parabolic reflector.

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

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

In 1826, the Liverpool to Holyhead telegraph was set up. This was an optical telegraph, based on a new semaphore system devised by Lieutenant Barnard Lindsay Watson. It comprised a chain of semaphore stations at Liverpool, Bidston Hill, Hilbre Island, Voel Nant, Foryd, Llysfaen, Great Ormes Head, Puffin Island, Point Lynas, Carreglwyd, and Holyhead, a distance of 72 miles.  It was capable of relaying a typical message from Holyhead to Liverpool in a few minutes, and a very short message in less than a minute. This was the first telegraph in Britain to carry commercial and private correspondence. Watson’s code was a numeric one: each station in the 1826 telegraph had a massive semaphore mast about 50 feet tall, each pole had three pairs of movable arms, and each pair of arms could signal a single digit. The 1841 telegraph had a two masts each with two pairs of arms, and a larger vocabulary of 10,000 words.

All of these systems were made obsolete by the inexorable march of technology. Last to arrive and first to go was the optical telegraph,  which was superseded when the electric telegraph linking Liverpool to Holyhead was finally completed in 1861, the first cables having been laid in 1858. Next to go were the signal flags. The Sea Lights were superseded by navigational buoys, which had the virtue of being moveable. By 1908, when the Lower Sea Light at Leasowe was extinguished, the sandbanks had shifted to such an extent that the Horse and Rock Channels were barely navigable, and the Sea Lights no longer provided a useful leading line. The Upper Sea Light on Bidston Hill shone alone for another five years, until sunrise on 9th October, 1913.

Radio is another form of communications that depends on line of sight. The principle of propagation of electromagnetic waves was discovered by James Clerk Maxwell in 1873, the same year that the present Bidston Lighthouse was completed. Marconi won an important patent in 1896, and built the first radio station on the Isle of Wight in 1897. Then it really took off.

At Bidston Lighthouse (and Bidston Observatory), radio antennae of all kinds have been installed at one time or another. Mersey Docks ordered a set of “Marconi Apparatus” for Bidston Lighthouse as early as 1908, but the Marconi Company failed to deliver, and the order was withdrawn. An antenna, probably marine, is still attached to the north face of the lighthouse tower. Amateur radio enthusiasts, notably the Wirral Amateur Radio Society, still operate from Bidston Lighthouse on annual International Lighthouse and Lightship Weekends, and other special occasions. Our webcam is brought to you over a line-of-sight wireless network. In 2014, Wirral Radio 92.1 FM moved their transmitter to Bidston Lighthouse.

Line-of-sight communications are as much a part of the future of Bidston Lighthouse as its past.

Seamen’s Wives

Bidston Signals on ceramic jug

Bidston Signals on ceramic jug

In the twenty first century, we take electronic communications for granted. Most of us can’t remember a time without radio, telephone, and television. Email, text messages, twitter, social networks are part of our daily lives. We’ve almost forgotten about telegrams and fax machines. No-one living today was around when the Bidston Hill Signals were the state of the art in communications.

It is difficult for us to imagine today just how important the Bidston Signals were to the people of Liverpool. News of the imminent of arrival of ships into port was valuable enough to justify building more than one hundred flagpoles along the ridge of Bidston Hill, and paying teams of workers to operate them. Later on, the Liverpool to Holyhead telegraph was established, with pairs of semaphore masts were placed at relay stations on Bidston Hill, Hilbre Island, and so on, all the way to Holyhead. The signals were truly a part of popular culture, and even featured on mundane items of pottery.

What a sight it must have been! This is how Albert Richard Smith described Bidston Hill in 1848, in his book The struggles and adventures of Christopher Tadpole at home and abroad:

But the sight was so riveting that he could not take his eyes from it scarcely, even to notice the lighthouse under whose very walls they passed, with its array of signal-masts that looked as if somebody was either preparing a great display of fireworks, or making ready to set sail and carry the entire hill, lighthouse, telegraph and all, out to sea upon the first fair wind.

“That’s a curious thing,” said Hickory, as he pointed to the telegraph. “I’ve heard there’s people that can read that gibbet just like a book. I never could, not to speak of. I’ve made out a F, and a L, and a E without the middle, and sometimes they was upsy-down. And once I saw it trying uncommon hard to turn itself into a H, but it wasn’t much of a go, not to speak of.”

But most poignant of all perhaps is this account of a sailor’s wife, who looked anxiously to the Bidston Signals for news of her husband:

I have frequently seen a very particular friend of mine, a sailor’s wife, who considers herself, occasionally, the happiest woman in the world, watching the wind, from “sou’ sou’ east—nor’ nor’ east—east and by no’th,” and, with a pair of compasses, leaning over a large chart, endeavouring to trace her husband, by counting the days, and allotting so many degrees of longitude and latitude to each day, to the extent of the voyage; and have whispered to her, in her calculations, “wind and weather permitting.” I have seen this very happy woman pace the room at midnight, if the wind ever attempted to blow from an adverse quarter, and have reasoned with her about

“The sweet little cherub that sits up aloft,
To keep watch for the life of poor Jack”

I have even seen her turn tide-waiter, and count the poles on Bidston Hill, on which a flag on the top announced from the Lighthouse that the expected vessel was in the offing. In another state of her happiness, I have heard her heart beat, when, in looking through the telescope, she dreaded lest, among a sickly and reduced crew, he should not be there; and have been present in another felicitous moment, when the report came, that all was lost, yet was she, occasionally, very happy!

From “Seamen’s Wives”,  in SKETCHES IN PROSE AND POETRY, by Katharine Head, Kirkdale, Liverpool, 1837.

Lighthouse Passports

The International Lighthouse Passport scheme was launched last year by Lizard Lighthouse Visitor Centre. Similar schemes have proved popular in North America.

Passport holders collect ink stamps from lighthouse visitor centres. Each page has space for one lighthouse stamp and additional notes so that you can also use it to keep a record of your visits.

Lighthouse Passport with stamps for Bidston and Leasowe.

Lighthouse Passport with stamps for Bidston and Leasowe.

In Wirral, Bidston, Leasowe and Hilbre Island Lighthouses all have lighthouse stamps and limited stocks of lighthouse passports for sale.

The Association of Lighthouse Keepers maintain a full list of lighthouses with passport stamps.

The passport stamp for Bidston Lighthouse is based on a line drawing by Phil Ryder. Thanks, Phil.

Bidston Lighthouse Passport Stamp

Bidston Lighthouse Passport Stamp

Mortimer 1847

Here is an extract from “The History of the Hundred of Wirral”, by William Williams Mortimer, 1847.

Bidston Lighthouse is an object very familiar to the inhabitants of Liverpool, and is one of the localities which command attention, as much from its prominent appearance as its mercantile utility. The Corporation of Liverpool having obtained an Act of Parliament, authorizing the purchase of Bidston Hill and the erection of a Lighthouse upon it, an edifice for that purpose was built in 1771. It consists of a substantial stone building with an octagonal tower, which from a distance has the appearance of a church, and is frequently taken by strangers for one. A long range of poles were formerly placed on the ridge of the hill, on which signals were hoisted to announce to the merchants of Liverpool the approach of their shipping; but the establishment of a line of telegraphs, from that town along the coast of Wales to Holyhead, has nearly superseded the old mode of communication. But as the lights, from their elevated position, are visible for a circle of fourteen miles, and blending with those at Leasowe Lighthouse, point out the entrance into Liverpool, the continuance of the establishment is indispensable for the safety of the numerous shipping trading into that port.

The Lighthouse of Bidston is deserving a visit, and the stranger will be amply gratified, not only with its construction and appendages, but with the varied and extensive prospect which is obtained from a small gallery that projects round the upper storey of the tower, at an elevation of three hundred feet above high-water mark. To the westward, the marshes, a plain of upwards of five hundred acres, on which graze more than a thousand head of cattle, lay extended beneath the eye of the spectator, protected from the inundations of the sea by a range of sandhills and an artificial embankment, which cause the numerous vessels in the Rock Channel to have the appearance of sailing on dry land.

 

Catoptrics

William Hutchinson, Liverpool Dockmaster, revolutionised lighthouse optics with the introduction of the parabolic reflector. He conducted experiments at the Bidston Signals Station during the 1760s, and subsequently installed reflectors in the Wirral Lighthouses. He writes, in his Treatise on Practical Seamanship:

“We have made, and in use here, at Liverpool, reflectors of one, two, and three feet focus ; and three, five and a half, seven and a half, and twelve feet diameter ; the three smallest being made of tin plates, soldered together ; and the largest of wood, covered with plates of looking glass”.

Hutchinson installed the largest one at Bidston Lighthouse, which was furthest from the sea. The large reflectors had some problems: they used a lot of oil, and smoke from the wick tended to obscure the reflector. Eventually, it was found that several smaller reflectors, arranged so that their beams were parallel, gave an equally bright light and used less oil.

Trinity House have an eighteenth century parabolic reflector in their collection. Its diameter is twenty inches.

18th century catoptric reflector, in the Trinity House collection.

18th century catoptric reflector, in the Trinity House collection. Photograph courtesy of the Corporation of Trinity House.

Little is known about the provenance of this reflector, because, sadly, Trinity House was bombed in 1940, and many of its records destroyed. The reflector will be on display at the National Maritime Museum in Greenwich from March 2014 until January 2016.

Trinity House is 500 years old this year. Henry VIII granted a Royal Charter to Trinity House in 1514.

Most of the lighthouses of Liverpool Bay were built and run by the port of Liverpool, not Trinity House. The Mersey Docks and Harbour Board took over from the Liverpool Dock Trustees in 1858. It was not until 1973 that Trinity House took over Hilbre Island Lighthouse and Point Lynas Lighthouse from the Mersey Docks and Harbour Board.

Catoptric lights are based on the principle of reflection. They were eventually superseded by dioptric lights, based on the principle of refraction, thanks to the work of Augustin-Jean Fresnel. When Bidston Lighthouse was re-built in 1873, it was equipped with a Fresnel lens manufactured by Chance Brothers.

Acknowledgments. My thanks to the Corporation of Trinity House and Neil Jones, Archivist, for permission to use the photograph of the catoptric reflector.