Astronomer Visits Impressive, But Not Famous, Park in a Foreign Land

The Muniment Room of the Birr Castle Archives, August, 2010. This was my "office" while researching connections between the 19th Century Parsons family and America. (90-degree panorama of several handheld vertical frames -- should be clicked on and viewed large.)

The astronomer of this post's title isn't me, who traveled from Santa Cruz County, California, to County Offaly in Ireland in 2010. The astronomer in question is one who traveled exactly the other way, from County Offaly, Ireland, to Santa Cruz County, California, in 1891.

Laurence Parsons, Fourth Earl of Rosse, as a Young Man (photo from the Birr Castle Archives)

The Fourth Earl of Rosse

Had he not been surrounded by superluminous immediate family members, Laurence Parsons, the Fourth Earl of Rosse, probably would be considered among the top tier of Irish scientists and engineers of the 19th Century. He directed the great astronomical observatory in Parsonstown (now Birr) Ireland, including the largest telescope in the world, for more than 30 years. He pioneered the use of infrared sensing techniques to measure the temperature of the surface of the Moon. He was an officer of the Royal Society (and delivered its supremely prestigious Bakerian Lecture on Physical Science in 1873) and was Chancellor of Trinity College, Dublin, for more than two decades.

The Fourth Earl inspects a 36-inch telescope at his observatory, late 1800s. This particular telescope no longer exists, but the walls in the background -- support structure for the giant "Leviathan of Parsonstown" -- still do. Between them now is a reconstruction of that revolutionary instrument, designed and built by the Fourth Earl's father. (Photo from Ireland's Historic Science Centre, Birr Castle Demesne.)

And yet, in his own living room, he was overshadowed from a number of directions: his father, William, the Third Earl, essentially invented the single most important tool of extragalactic astronomy (the giant reflecting telescope) before we even knew there was such a thing as "extragalactic astronomy." His mother, Mary, was a pioneer in the infant technology of photography. His youngest brother, Charles, was a prolific inventor who revolutionized transportation technology by inventing the steam turbine -- and demonstrated it in daring fashion to the British Admiralty by bringing his turbine-powered yacht, the Turbinia, uninvited, to Queen Victoria's diamond jubilee in 1897 and outrunning the finest ships of the Queen's Navy that tried to catch the gate crasher. (There is a great action photo of the Turbinia running the Royal Navy silly here.) His cousin, Mary, was a pioneering microscopist, and one of only three women on the mailing list of the Royal Astronomical Society at the time. The other two were Mary Somerville (after whom Somerville College at Oxford University is named) and Queen Victoria herself.

One of the Fourth Earl's travel diaries in the Birr Castle Archives, 2010.

Unlike his revered father and mother, though, Laurence became a world traveler (presaging the globetrotting ways of his grandson and great-grandson in their pursuit of botanical specimens and, in the case of the current Earl, service to humanity through the United Nations). His two long tours of North America, one in 1884 and the other in 1891, are the first instances I can find of his family's venturing into the Western Hemisphere.

Sherwood peruses the archives, Birr Castle, 2010. The white cotton gloves are to protect the old paper from skin oils and acids.

I came across his handwritten travel diaries for those two trips in the Birr Castle Archives in August, 2010. His notes on his second trip, the one in 1891, contained one thing that made the hairs on my forearms stand up in eerie astonishment, and another that is deeply puzzling. Both concern events in places less than 50 miles from my home in Boulder Creek, California -- one of them very, very much less than 50 miles -- almost half way 'round the world from his home in the Irish midlands.

A pair of pages from the Fourth Earl of Rosse's travel diary, 1891.

An Astonishing Personal Co-Incidence

A new generation of research astronomical observatories had barely begun in 1891, incorporating a revolution in location rather than technology. Lick Observatory of the University of California was the first mountaintop research observatory in the world, having gone into operation only three years before in 1888. (Before then, the benefits of good "seeing" afforded by certain mountains' steady airflow, diminishing the wavering scintillation or "twinkling" of starlight, had not been widely recognized.) Lick is located atop Mt. Hamilton, just East of San Jose, California, and is a place dear to my heart. It is also only about an hour's drive from my office at DeAnza College.

Lick Observatory at the summit of Mt. Hamilton, California, September 2008. The great 36" refractor still occupies the big dome; the Ft. Harrington pickup truck squats near the entrance.

Clearly, Lick Observatory would be a necessary stop for the Director of the famous Leviathan of Parsonstown on his tour of North America in 1891, and it was. Laurence Parsons, Fourth Earl of Rosse, arrived in Northern California (by train via Mexico and Los Angeles) in March, 1891. His diary entries concerning his trip to the mountaintop are full of technical detail, but short on context -- and short on something else that I'll get into later. The real immediate surprise to me was about something closer to home. Literally, closer to home.

Shortly after his visit to the top of Mt. Hamilton, he wrote these entries in his diary concerning an excursion to another Northern California attraction:

Sunday (Easter) [March 29, 1891]
Sorry I was taken out by 10-30 train to Mr. Doyles (Menlo Park, a residential spot on the way to Sn Jose) so I missed Church. Holden [Edward Singleton Holden, first Director of Lick Observatory, founder of the Astronomical Society of the Pacific, and all-around hard guy to get along with --SH] & I lunched & dined with the Ds (Mr & Mrs two daughters & 2 sons) & between drove to the new "Stanford University" which as yet consists of buildings only, unfinished, in imitation of the old Spanish Mexican style. Went on to San Jose and stayed night at the new hotel.

Monday Mar. 30
Started at about 10 for "Big Trees" station on the narrow guage line. The "big trees" are close to the station. They are said to be not far short of 300 ft high but only half the girth of the Yosemite groves. I found it took 7 of my stretches to reach round one say 7 x 5 3/5 feet, 40 1/4 feet = say 12 3/4 diam at 4 feet from ground. [I love the way he "talks" himself through the arithmetic! --SH] In the inside of a hollow one my outstretched arms could not reach across the cavity. The branches are short & poor. The whole forest has contained many similar trees but they furnish the "red wood" which is used for all building construction in these parts (Sequoia Sempervirens: bot name). The wood is soft & not resinous yet very durable. Among other things it is used instead of stone or brick in the linings of the railway tunnels.

From there we drove on to Santa Cruz, a sea side resort with hotel & thence by rail to Monterey also on the sea coast...

Wow.

It is clear that on March 30, 1891, the Fourth Earl of Rosse visited the San Lorenzo Valley, the short notch in the Santa Cruz Mountains in which Boulder Creek and Ft. Harrington are located. The "Big Trees" and the narrow-guage railroad are the first clues -- the private park he refers to still exists as the "Big Trees and Roaring Camp Railroad" complex just outside the little town of Felton, California, just down the valley from Ft. Harrington, and directly adjacent to Henry Cowell State Park.

"Big Trees and Roaring Camp Railroad," 2005. My late son, Doug Harrington, holds his daughter, Grace, on his shoulder in front of a narrow-guage locomotive that may well have been operating when Laurence Parsons, Fourth Earl of Rosse, visited this place in 1891.

Henry Cowell State Park is where I walk my dog. It's Kelsey's favorite place in the whole world.

Kelsey in heaven. Or Henry Cowell State Park. To him, there's no difference.

After discovering this, and having talked to Lady Rosse about the great co-incidence, she searched through the family's photo albums and found one that included the Fourth Earl's visual souvenirs of his second trip to America. In those photos was this one:

In what is now Henry Cowell State Park, California, 1891.

... a place in Henry Cowell State Park that I walk Kelsey past every time we go, near the park's headquarters. The tilted trunk isn't there any more, nor are the people in their formal dress, but the grove is there. It wouldn't be so astonishing if this were a photo of a major tourist attraction, like Yosemite or the Grand Canyon -- but this is a little local park, a dog-walking place, that somehow is shared across the thousands of miles and the century between, and that thrills me. Maybe that's silly. I don't think so.

Sherwood photographing a photograph album from a trip by an astronomer of bygone days to his own present home. The multiple layers of self-referencing in this image make me dizzy.

A Deeply Puzzling Four Blank Pages

In addition to my astonishment on finding that the Fourth Earl of Rosse, all the way from the middle of Ireland, had visited my dog's park, I was intrigued by a curious set of four completely blank pages in his diary, between his arrival at Lick Observatory and his departure. Wasting paper like that was utterly unlike the Fourth Earl (not a single line of paper is blank elsewhere in his diary, and often he wrote things in the margins or gutter), but here were four empty vessels at the most crucial point in his tour (from an astronomer's perspective.)

The mystery will be the topic of a future post here in SherWords, once I have researched the matter in more depth -- which I can do, since the Lick Observatory Archives and the Astronomical Society of the Pacific both have their headquarters just a few miles away!

Stay tuned.

Whatever Shines

Mary Rosse's darkroom, Birr Castle, late 1800's.

John McCain and Barack Obama squared off again last night in the last debate before our Presidential election, and many "sound bites" were spat out by both sides, and will be hashed over and analyzed ad nauseaum elsewhere.

One that didn't get (and won't get) much attention -- because it's so predictable and so pablum -- was McCain's touting of his running mate as what he might call a "feminist": someone who has accomplished hard stuff about 50 years after someone of the other gender could have accomplished it. Good for her. Really.

But wouldn't a real feminist superheroine be one who breaks a barrier before some dude cracks it? Like maybe the Irish gals whose audacity is recounted in Whatever Shines Should Be Observed, a slender tract by Susan M. P. McKenna-Lawlor.

Whatever Shines Should Be Observed, part of Kluwer Academic Publishers' Astrophysics and Space Science Library, tells the stories of five remarkable Irishwomen who were pioneers in a variety of modern sciences and technologies. From the introduction by Alison, Countess of Rosse (the current Lady Rosse of Birr Castle):

This book gives us the lives of these five exceptional, but little known, Irish women. They achieved high recognition in scientific subjects at a time when women in the propertied classes were hardly allowed out of the nursery before their marriage, and schooling for daughters was very much an afterthought behind the education of their brothers. These five ladies, due to their own persistence and high intelligence, taught themselves astronomy, microscopy and photography, an unusual achievement in itself. But more than theat, they were to become experts in their fields and successfully pursued these ambitions, indeed, followed their stars. Mary Rosse won the Dublin Silver Medal for Excellence for her photography. Mary Ward [a cousin of the time's Lord Rosse -- SH] published authoritative works on astronomical subjects and microscopy and, by 1903, Margaret Huggins and Agnes Clerke were invited to become honorary members of the Royal Astronomical Society.

(Mary Ward has another, sadder distinction: she was Ireland's first auto accident fatality, thrown from [and run over by] a Parsons invention, the "Road Locomotive," on the grounds of Birr Castle on August 31st, 1869.)

Diane and I will be going back to Birr Castle, the home of the remarkable Parsons family, in 2010, and will be combing the archives of these astonishing people and their friends and cohorts in the castle's archives room, which we had an all-too-brief look at in 2006. Look forward to more then here in SherWords... we sure do!

The Seventh Earl

Brendan Parsons, Seventh Earl of Rosse, photographed in the Birr Castle archives room by Sherwood Harrington, August, 2006

In a comment on the entry "Cloudy Skies, Clear Genius..." ronniecat asks:

Is the current Lord Rosse as interesting and unusual as his predecessors?

Brendan Parsons, the Seventh Earl of Rosse, is a remarkable man in his own right (just take a look at this article from 2005 about his honorary doctorate from Trinity College, Dublin.) He is also a very charming man in person, and Diane and I are honored to have had the delightful experience of conversing with him and his wife, Alison, Countess of Rosse, in their home. (The current Lady Rosse is an accomplished artist -- see #s 45 and 46 in this index of works displayed in the current display at the Jorgensen Fine Art Gallery, Dublin, "A Century of Women Artists." But, of course, they are all accomplished at something or another to a degree that makes ordinary folks like me feel pretty mundane.)

Diane chats with Lord Rosse in the gathering evening twilight as he tends a bush by the banks of the Camcor on the Tipperary side of his Demesne.

His identity internally seems to be completely Irish, as befits someone whose ancestors going back seven generations have occupied the same house in the Irish midlands. I say this because for some the title "Earl" or "Lord" -- originating as they do in England -- seems superficially to token an English identity.

Some insights into Lord Rosse's thinking can be found in numerous quotes from him in Anne Chambers's 2000 book, _At Arm's Length: Aristocrats in the Republic of Ireland_. Here are just three: [Double quotes denote Chambers, single ones denote Lord Rosse]

[On his family's multi-generational eschewing of upper-class English schooling] "[He] maintains that if his ancestors had not bypassed the established route of an English public ["private" in American usage] school for an education at home, 'they would never have become famous scientists. They would have been turned into these sort of petty-minded bureaucrats who might have made good civil servants, but who would not have a flair for anything mathematical or scientific or any feeling of a wider world beyond the British Empire.'"

[Concerning the political future of the island] "Brendan Parsons feels strongly 'that we should and must be one country. It will be a gradual process but it will be a process of gradual elimination when the border will count less and less. It costs three billion pounds per year just to keep six counties of Irland half-British. They will soon be discarded by Britain who will get bored for paying for all that.'"

And, most poignantly, this concerning famine then and now:
"At Birr Castle today, the memory of the Famine has remained indelibly etched in the psyche of following generations of the Parsons family. The present-day Earl of Rosse has in more recent times had first-hand experience of the ravages of famine. For fifteen years he served with the UN as relief co-ordinator during the disasters in Bangladesh and the Sudan. The fact that his ancestor during the course of the Great Famine chose 'to employ the people creatively, earning a wage instead of enduring the ignominy of the soup kitchen,' is something that he himself endeavoured to put into practice during his tenure with the UN relief agency. During the Famine over five hundred people were employed on the estate at Birr, building everything from walls to bridges. 'I've now got over five and a half kilometres of wall and twenty-three bridges to keep up, thanks to all that,' Brendan Parsons muses ruefully.

A famine-relief work that the Parsons are still paying for: a "guardhouse," and a bridge over a moat that were built by townspeople during the Great Famine.

"Although the Famine happened over a century and a half ago, it is still close to the consciousness of all Irishmen. This, he maintains, is what 'enables us Irish to empathise with and have a closer understanding of the problems of famine in the world today. As I have seen in Bangladesh, the Sudan, Ghana and in other countries, the Irish command enormous respect because of the confidence they are able to gain of the local people in those situations.'

"He contrasts this with the attitude of some British agencies that come in and 'tend to try and impose their solutions and economic theories which don't work on the ground. You must identify with the problems of the people actually starving, give them a respect by adhering to their traditions and not try to turn them into something they are not.'"

Ronniecat, this man is a force. Yes, indeed, he is as interesting and unusual as his predecessors, and I wish the world had more like him.

However, since this blog seems to be running the risk of becoming a pean to the Parsons, I'm going to give them a rest for a while. Oh, right after I reply to Brian's comment real soon now.

(More of our pictures of the Birr Castle Demesne can be seen in this slideshow.)

Cloudy Skies, Clear Genius, and Lensless Telescopes

Commenting on this blog's post about M51 a while ago, and on Lord Rosse's giant (for the 1800's) 72-inch telescope, Mike Peterson said:

The next trick would be to create a formula that would evaluate, on the one hand, the optical properties of a lense crafted in 1840 compared to the potential for such a lense crafted with modern techniques ... and then compensate for the fact that the stars he was gazing at were only competing with candles and the occasional rush torch on earth.

Wow, where to start? I think I'll start with the last part:

I) Dark Skies, Short Nights

Lord Rosse's 19th century skies were certainly darker than 21st century, light-polluted views -- but he (and all others who used the Leviathan of Parsonstown) had two pretty bad things to deal with that most modern observatories don't: a far northerly latitude and Irish weather. The combination is deadly for observing.

Records from the seven decades when the Leviathan was a productive instrument (and the largest in the world) indicate that there were only about 60 to 70 nights a year when the sky was clear enough for any work to be done. (Interestingly, since the reconstructed Leviathan went into operation at the same site in 1997, the average is only about 35 to 40 -- but that may be due to a difference in perception of what constitutes "workable" rather than a real change in cloud cover.) Most of those would be in the summer -- when darkness was short.

That latter bit -- the shortness of summer nights -- came across clearly to me when reading a bit of correspondence in the Birr Castle archives room from J.L.E. Dreyer (then an observing assistant to the 4th Earl, who, like his father, was an accomplished astronomer) to his boss on June 9th, 1875. Dreyer reported to the 4th Earl (who was summering in one of his homes in England) that he had given a visiting dignitary a demonstration of the telescope the previous night, and that the visitor "... would not wait beyond 12 o'clock, as it would become light again almost at one." He goes on to explain to his boss:

Since I last had the honour to write to you, I have observed on 3 or 4 nights, but there has, of course, been very little work done, as the nights only are two hours long. I intend to leave [to visit home in Denmark] this on the 21st inst. [sic] in the morning and shall be back till [sic] the first of August. My quarter-salary will not be due untill the first of July, but under these circumstances I should be very much obliged, if your lordship would not object to hand me a check for the portion of the quarter already past. Yours very truly J. Dreyer

In other words, no work's gonna get done here until August, anyway, Earl, so I'm gonna go home. Please pay me.

(At least one person who reads this blog will recognize the place of J.L.E. Dreyer in the recent history of astronomy. For those who don't, you might want to click here.)

Here are the last two pages of the letter quoted above:

(Click on the images here to see -- it is hoped -- larger and legible images. Please e-mail me if they're not legible, and I'll upload bigger image files.)

That's my finger at the top of the right-hand image. The current Lord Rosse is not terribly enthusiastic about digitizing the Castle's archives, but he's being worked on. Meanwhile, treasures like this have to be photographed one at a time, without flash, by those of us lucky enough to stumble into the opportunity.


II) Mirrors vs. Lenses
Addressing Mike Peterson again: Mike, you implicitly questioned the quality of a telescope lens crafted in the 1840s compared to a modern one. No problem here: the only lenses in the Leviathan were little ones in the eyepieces.

The Leviathan's main light-gathering element was a 72-inch wide metal mirror, a mammoth expansion on an idea first put forward by Isaac Newton in the late 1600's: that a concave paraboloid mirror could focus light just as well as a lens, but at half the effort (because only one surface, not two or more, need be accurately shaped.) Reflecting telescopes would not become common in research astronomy until almost a century after the Leviathan was built, though, because of difficulties in maintaining the reflective surface (the current process of misting aluminum onto carefully-shaped glass wasn't developed until the 1920's) and because of simple, human inertia among the professional astronomical community. Reflectors were... well... just weird. Lord Rosse wasn't constrained by such community biases because he wasn't a member of that particular community -- at least he wasn't until his observatory became a prestigious place for members of that community to gain employment!

The Leviathan's mirror was of a kind never before fabricated on such a scale, and seldom attempted since: a solid metal, speculum mirror. Facilities to forge and shape the mirror had to be first invented, then built, and then operated on the castle grounds. The Third Earl (and his wife, Mary, a pioneer in photographic image processing) did all of that, and their efforts (and the sheer spectacle of their operation) engendered the following bits of florid prose among many others on display in the Birr Castle Demesne's museum:

From T. R. Robinson, Director of the Dunsink Observatory, in 1842, accounting a nighttime operation of the speculum forge:

On this occasion, besides the engrossing importance of the operation, its singular and sublime beauty can never be forgotten by those who were so fortunate as to be present. Above, the sky, crowded with stars and illuminated by a most brilliant moon, seemed to look down auspiciously on their work. Below, the furnaces poured out huge columns of nearly monochromatic yellow flame, and the ignited crucibles during their passage through the air were fountains of red light, producing on the towers of the castle and the foliage of the trees, such accidents of colour and shade as might almost transport fancy to the planets of a contrasted double star. Nor was the perfect order and arrangement of everything less striking: each possible contingency had been forseen, each detail carefully rehearsed; and the workmen executed their orders with a silent and unerring obedience worthy of the calm and provident self-possesion in which they were given. [SH: the fuel for the forge's spectacular fires was, of course, peat. This, too, is unique in the history of astronomical technology!]

From an anonymous account in the King's County Chronical [sic] (County Offaly was called King's County from the plantation time until the establishment of the Republic), it is clear that the Earl himself was viewed in a heroic light as well:

I saw the Earl, the telescope maker himself -- not in state, with his coronet and ermine robe on, but in his shirt sleeves, with his brawny arms bare. He had just quitted the vice at which he had been working and, powdered with steel filings, was washing his hands and face in a coarse ware basin placed on the block of an anvil, while a couple of smiths sledging away on a blazing bar on another, were sending a shower of sparks about his lordship which he little regarded as though he were a "Fire King". This was in a spacious, rude, smithy which almost occupies one side of the court yard of the castle and in which not only were swing bridges and force pumps, and tackle for scientific instruments constructed, but common and everyday articles in the shape of agricultural gates, sub-soil ploughs, etc, for use on his farms... As he drew on his coat... the Earl looked an intelligent foreman..." [SH: The true heroism of the Third Earl and, especially, his wife Mary would not become evident for a couple of years -- when the famine hit, and all astronomical operations were suspended while they devoted their efforts to famine and economic relief for the village of Parsonstown, now Birr.]

The last bit of the quote about "swing bridges and force pumps" refers to the Parsons family's already well-established reputation for engineering innovation; the "swing bridge" is the Demesne's suspension footbridge across the River Camcor (an innovation of the third Earl's father, and possibly the first modern suspension bridge in the world) and "force pumps" refers to the Parsons' re-directing of the River Camcor to better configure their Castle's Demesne.



III) Restoration of the Leviathan

The giant telescope fell into disuse, then disrepair, then rot, then oblivion after the death of the Fourth Earl, and World War I, and the subsequent shift in the passions of the Parsons from astronomy and engineering to botany. The current Earl of Rosse, Brendan Parsons, is a world-renowned arborist (having worked for thirty years with the UN on various reforestation projects in third-world countries), but he also has a keen understanding of the remarkable place his family holds in the recent history of science and technology. He orchestrated the construction of a replica of the Leviathan in the 1990's, a project that came to fruition ten years ago. Here's a picture from the Castle Museum of the new tube being backed in to the main gates:

... and here's one of the reconstructed Leviathan from behind in August of 2006 (the new mirror is at the end of the tube closest to us in this picture):

Inside the black box at this end of the tube is a replica mirror -- but not a speculum metal mirror. While the effort to reconstruct the telescope was aimed at being as faithful as practicable to the Third Earl's original design, a speculum disk of that mammoth size was prohibitively expensive, so cast aluminum was used instead. That caused problems: aluminum isn't as heavy as speculum, so that caused all kinds of problems balancing the finished instrument.

Those sorts of headaches were dealt with admirably by the chief engineer of the project, Michael Tubridy, a civil engineer of great prominence in Ireland (he was chief of the project to construct Dublin's newest airport terminal, for example.) "Chief" is an appropriate word, by the way: Michael Tubridy was also the original flautist for the Chieftains.

It's all so, well, Irish, isn't it? A tale of great achievement, little-recognized in the larger world, and basically futile, anyway (the world's largest telescope built where it can't really be used?), a work that spans five generations and is revived by a musician, and a tale that can only be gotten through with the help of liberal sprinklings of Guinness. Perhaps. Truth be told, I haven't really tested that last bit.

And this is far from even a thumbnail account of the Parsons' story. That's a book, not a blog entry.

A Galaxy and Bastard Jacobite Cannon Balls

M51 (the "whirlpool galaxy") is the bright centerpiece of a relatively small cluster of galaxies, a neighbor to our Local Group, and a fellow member of the Virgo Supercluster. It's roughly 30 million light years away, and is seen face-on from our perspective. It is actually a pair of galaxies, the larger, spiral M51A (or NGC 5194) and the smaller, irregular M51B (or NGC 5195). It is a spectacular sight at almost any resolution, but astonishingly so as seen through the Hubble Space Telescope:

(A larger, higher-resolution image can be downloaded by clicking here... and a truly massive [more than 100 megs!], full-resolution file is available here -- but please come back!)

One of the first people to recognize the spiral structure of M51 was William Parsons, the Third Earl of Rosse, who built the world's largest telescope on his estate in the midlands of Ireland in the early 1840's. His ingenious 72-inch telescope, "The Leviathan of Parsonstown," was to remain the largest (and thus most powerful light-gatherer) on this planet for more than 70 years, a record of persistant dominance not likely to be equalled. Its staggering light-gathering power for the time allowed Lord Rosse to view detail in objects too faint for others' instruments.

The reconstructed Leviathan of Parsonstown in August, 2006.

Two of Lord Rosse's drawings of M51, done at the eyepiece of the Leviathan, on display in Ireland's Historic Science Centre on the grounds of the Birr Castle Demesne, home to the Third Earl of Rosse's great-great grandson, Brendan Parsons, the Seventh Earl.

M51 permeates the traditions of the Birr Castle Demesne, as Diane and I found during our stay there in August of 2006. In fact, a major, relatively new, facet of the Demesne's lovely and extensive gardens is the "Whirlpool Spiral," a modern variation on the ancient garden maze. It is a spiral of mown pathway and lime trees, laid out in porportion to imitate the appearance of M51A and M51B. I haven't been able to locate an aerial view of the spiral, but here it is in part of the Demesne's visitors' map:

(The spiral is number 13 on the map; number 2 is the reconstructed telescope.)

At the center of the spiral of young lime trees -- at the core of the verdant M51A -- is this pit at the left of the frame:

When I asked the current Lord Rosse about this odd depression, he told me that it was a "siege pit," a place where Jacobite cannon under the command of the Bastard Duke of Berwick were entrenched during the 1600s' War of the Two Kings. Balls from the cannon left marks on Birr Castle that are still visible, and some of the balls compose part of a foyer decoration:

While supermassive black holes at the centers of galaxies may be commonplace, M51 is the only one I know of with a siege pit at its core.

A short slideshow of the Birr Castle Demesne from our visit in August, 2006, can be viewed by clicking here.