Investigation of a round brick lined Blue Water Pool at Torwood near Dunipace and Larbert

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Local Mystery

The Torwood Blue Water Pool

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27 October 2011
Mining Consultant Assesment

15 October 2011
Video inside Arch Chamber

25 June 2011
New photos in Arch.
Chamber could be large.

1 June 2011
First Photos inside Brick Arch
Airshaft Theory shaken.

20 March 2011 Extra
Why aint the Pool Blue?

20 March 2011
Son of Blue found at Carbrook

8 February 2011
A Summary of what we have so far and the start of page 2.


composite blue pool


Summary February 2011

Known by Denny folk as The Blue Pool and by Plean folk as The Blue Water — I created a hybrid title, The Torwood Blue Water Pool.
After two years of investigating and a lot of phone calls and interviews, I concluded that there is nobody alive today who knows its original purpose.
Many ideas have been suggested and at one point I was sure it was a water storage header tank supplying either Torwood and Larbert or the very large Calico Print works at Denovan.
I contacted Scottish Water who very kindly did some archive searching and concluded that they have never had any assets in the immediate area of the Pool.

The circular Pool is flush with ground level, 6 metres in diameter and 5 metres deep. The wall is three bricks thick and surrounded by a waterproof layer of clay. The smooth engineering brick is red in colour and has no company markings. The cement joints between the bricks are in excellent condition.

The oldest and most common theory is that the Pool was something to do with a mine.

Its remote location and lack of rail or decent roads would rule out a manufacturing concern.

The very high build quality would probably rule out a Lime or Charcoal Kiln.

The location is at the highest point for miles around (other than Tappoch Broch) and would certainly supply a good draught for a short chimney.

The theory that I am currently considering is that it was an Air Shaft for a Mine, but what Mine?

To the south was Herbertshire Colliery (The Station Pit) at Denny and to the north was Plean Colliery.
Central Scotland’s coal field is fractured by many geological fault lines that tend to run from west to east.
When a Pit Shaft was sunk to the coal seam, tunnels went out in all directions until they hit a fault line that marked the limit of the field.

Two well known fault lines cut off both Herbertshire and Plean Collieries from our Blue Water Pool.
There is a Clay Drift Mine about half a mile to the north. It was owned by the Bonnybridge Silica & Fireclay Co Ltd and it opened in the 1940s. The Torwood Blue Water Pool appears on a map dated 1928 though I feel sure it is older than that.
There is a very old Lime Drift Mine to the south east but I am discounting that for the time being.
The only remaining Pit was Quarter Colliery. Just south east of Quarter House and on the north side of the Dunipace to Plean road is the remnant of a Pit Bing and this was the location of Quarter Colliery number one shaft.
The pit was operated by William Baird of Gartsherrie and started working Ironstone in 1865. Production switched to Coal around 1880. There was an explosion in 1895 that killed thirteen men and the Colliery shut down completely in 1910.


In 2009, having decided to solve the mystery of its purpose, I rediscovered the Pool. It was a sad looking dark hole that was almost overgrown by trees. The internal brick wall was covered in a dark thick weed and there was none of the vibrant blue colour that originally gave the pool its name. A lot of debris had accumulated on the bottom which was covered in dark silt and weed.
There was no sign of a brick arch that I remembered from my youth.
I set to work clearing the weed and uncovered the brick arch at the bottom of the Pool. It was much larger than I remembered and was pointing towards Quarter Colliery coalfield.
I also found three clay pipes around 13 centimetre diameter that broke through the wall about one metre below the surface.
There was also a 3 centimetre diameter iron pipe stub about 4 metres down and lining up with a manhole about 11 metres to the east.
Finds were made to the east of the manhole. Curved iron flat-bar and OG rainwater guttering custom built to the curve of the 6 metre diameter pool. Flat roofing slates and common half-round guttering were also found.
I now had a lot of pieces but did they all belong to the same puzzle?


A local from Torwood village remembers the Game Keeper in 1960 describing how the pool used to have a Beehive roof that had since fallen in and the loose bricks were clearly visible on the bottom.
About six long planks of wood (the size of rafters) were playthings for the children, many of whom regularly swam in the Blue Water.
I also heard a whisper that someone had family memories of grandparents who worked in a large house and accompanied the gentry to the Pool which they used as a Spa. I would really like to hear from those people.

If the original purpose was an airshaft, it would have been a short chimney about two or three metres tall.
Once redundant, the bricks would have been spirited away for use in another project, leaving the present pool flush with ground level
— but a chimney would not have had a beehive roof or OG guttering and that is why I suspect there has been a change of use during its lifetime.

I would like to propose the following possibility

Much of this is


In 1910 when Quarter Colliery ceased operation, the workings would have flooded with ground water that worked its way up the ventilation tunnel to the arch and filled the base of the short chimney with crystal clear water.

The ground above Quarter Coalfield is nearly 10 metres higher in elevation than the ground level at the Blue Water Pool. This could account for the almost constant overflow of water at the Pool — even when lower points around the Pool are dry. The flow averages about the same as a domestic bath tap.

3d Graphic Airshaft  

At this time, Torwood was owned by the Bolton family of Carbrook House near Torwood village. Maybe a young enterprising Bolton decided to make use of this free resource and convert it to a spa pool that he may have been familiar with in his military travels abroad.

A beehive roof is built to keep out the rain which collects in the rather expensive custom built OG guttering which may have been produced at Carron Iron Works.

A door is cut in the side and and a board is fixed to allow easy access and egress (getting oot again). They are almost ready for a dip but the water is freezing cold.

A building is constructed nearby to house a small boiler to produce steam that would be injected at the bottom of the pool through a 3 centimetre iron pipe and bring it up to a genteel temperature.
The valve for opening the steam flow is in the manhole.

This support building has a conventional timber framed roof clad with flat slate and is fitted with traditional half round iron guttering. At the end of its life, this building is also dismantled so the materials can be used elswhere.

3D Graphic Spa  

In 1914, The Bolton family sold Torwood. In the years that followed, the beehive roof collapsed and the chimney wall, above ground, was spirited away so the bricks could be used elsewhere.

The airshaft chimney come spa was now just a pool of lovely clear water and a free resource for local farmers who install two clay pipes pointing west and one pointing east.
At a depth of one metre, these pipes will give a reliable year-round supply for cattle troughs or even irrigation.

The water quality has been tested and the results are a rather unremarkable very soft water. Readings for Aluminium and Manganese were higher than normal.

Craig MacAdam, from Buglife Scotland, tells me that the high aluminium content could be caused by decaying peat.

3D Graphic Blue Pool


The above SPECULATION is certainly NOT a CONCLUSION
but may provide material for ‘Brainstorming’ and memory-jolting. If you have any relevant memories, please get in touch. I look forward to putting up the big brass plaque saying Case Closed.

The biggest clue we have at the moment is the Brick Arch. If I can get a camera down there and the arch tunnel goes as far as the eye can see, then it is almost certainly an air tunnel. If it stops after a metre or so then a major rethink is required.

The Blue Water Pool then became a curiosity and a popular swimming hole for the more adventurous local children.
Most people in the surrounding areas have never heard of the Blue Water Pool.
It was a special magical place, known to a select few (mostly children) and unseen by casual walkers on the nearby path from Denovan to Torwood village.
In the past two years, ‘Awareness’ has increased considerably.

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Update 20 March 2011 — Son of Blue

It was May 2010 when David Hunter of Torwood announced in the comments section that he had found an identical pool at Carbrook. David and his wife Stephanie had been researching Carbrook House. As they walked the grounds, they spotted a ring in the grass that had been missed by locals who had lived all their lives in the area.

They started scraping and soon uncovered the circular shaft with a wall of three bricks thick but it was full of earth — so no way of knowing if there was a Brick Arch. There was a nearby manhole, also full of earth.
The internal diameter of the shaft is a rather quirky 19 feet 7 inches whereas the Torwood Blue Water Pool is a perfect 20 feet.

Carbrook House  

This shaft was right above the entrance to the (north) Carbrook Clay Drift Mine. Jones Saw Mill once occupied the Carbrook grounds but now only a few concrete machine plinths remain. A local man who has lived much of his life in the area had a story that the shaft was a creosote tank for soaking timber.
The nearby manhole, was saturated with a tarry residue that had similarities to creosote.

It was time to separate the facts from the red herrings and Stephanie started to think it might be a Gasometer for storing coal-gas. This might account for the tar residue in the manhole.

map glenbervie

About a mile to the east is Glenbervie House and we know that in 1850 it had its own Gas Plant to, presumably, fuel the new gas lighting. Carbrook could quite reasonably have had its own Gas Plant.




coal gas plant

Stephanie found the following drawing of a coal gas manufacturing plant from 1911 and reckoned the shaft may have been filled with water. A bell shaped lid would rise and fall as the gas flowed in the goesinty and out the goesooty.

Then came the proof. A 1910 Ordnance Survey map showed not one but two Gasometers. Well done the Hunters — investigation closed — after they find that second shaft! The Gasometers were built long before the Carbrook Drift Mine — strike one red herring.

Perhaps understandably, Stephanie is not a great fan of my Airshaft theory for the Torwood Blue Water Pool and she suggests a possible Gas Plant for a nearby large House. The nearest house is Denovan but it is 1 kilometre away. Carbrook is 132 metres and Glenbervie is 248 metres from respective gas plants — both are next to their stables


The strongest argument for the Airshaft is simply that the Brick Arch points towards Quarter Colliery number One Shaft.
The snag is that it is fully 1.6 kilometres from the production shaft. The later shaft, Quarter number Two Shaft has its own Airshaft just a few steps away.

Was Torwood chosen for its height to produce a good natural draft before they had electric fans? — there is at least one wee snag.
The Dales Wood stands just North East of number One Shaft and is 10 metres higher than the Blue Water Pool ground level. Dales Wood would seem to be a more sensible location for a natural draft Airshaft.

Hopefully there are more clues and facts to be discovered. My next job is a photo up the Brick Arch.

Read on to discover the 'Blues'.

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map Carbrook  

20 March 2011 Extra — Why aint the Pool Blue?

Pure water has no colour. Water can contain minute suspended particles that affect the colour. Water draining from peaty ground may have a slightly yellow hew. Water containing a fine suspension of clay particles has a milky or opal blue colour.
Water absorbs and selectively filters white light which is made up of all the colours in the rainbow. Long wave Red Light is absorbed much more than short wave Blue
The further light travels through water, the more blue it becomes. Travel down into the deepest ocean and eventually all light will be absorbed, leaving total blackness.

ocean light rays weed  

In the 1960’s the Torwood Blue Water Pool deserved its name as the light coloured brickwork reflected a lot of light back up to the viewer’s eye. The Pool is 5 metres deep so the light travels 10 metres through the crystal clear water and comes back with a genuine blue colour — not milky but crystal clear like a blue diamond.


swimming poolToday the bottom of the Pool (and a fair way up the sides) is covered in very dark silt and weed. This dark surface absorbs ALL light indiscriminately and only a small amount of light makes it back to the surface.

The dark green colour has a lot to do with reflection of the green trees growing almost over the pool. The occasional stunning blue is a reflection of the blue sky.

If we cleaned out the Pool and painted the brickwork white, we would have the most stunning of crystal clear Blue Water Pools.

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1 June 2011 First Photos inside Brick Arch

Armed with an underwater camera, I had hoped to find an arched-roof tunnel going as far as the eye can see and descending at an angle of about thirty degrees in the direction of Quarter Colliery.

A similar arrangement can be seen in a photo of an Airshaft at Muiravonside Pit:

From Falkirk Museum & Archives (opens in new window)
View of a shaft sloping at a shallow angle into the ground. It is lined with bricks with an outer cement coating, and terminates in a brick arch.
Text on original print - "Air pumping station. 26/958 760. Showing brick lined air shaft."

muiravonside pit

inside arch 1 inside arch 2  

The Torwood Blue Water Pool's Brick Arch was heavily choked with weed but I managed to get an interesting detail.
The Arch is just an opening in the circular wall containing the pool. Behind the arch on the left hand side can be seen a plain brick vertical wall that appears to be higher than the arch. My Airshaft Theory may be looking a bit shaky.

As time permits, my next task will be to clear the weed inside the arch, with special attention to the vertical space just behind and above the arch. When the water clears (probably a week) I will try for some more informative photos.
Weed re-growth on the inner wall of the Pool has now obscured the three 5 inch pipes — I will uncover those.

During my sub aqua exploits, John Gillespie from Denny appeared on the scene. John, a very fit 70 year old, remembers visiting the pool when he was about 14 years of age.
John recalls with absolute certainty that around 1954 there was a continuous wall about 5 feet high going all the way round the pool. There were no breaks and the only way he could see the water was to pull himself up to look over the wall.
My own memories of around 1962 were of a ragged broken wall with bits about 3 feet and bits at ground level but I was not sure if I was inventing the memory. I certainly remember kneeling at the side of the pool and watching beetles swimming all the way to the bottom.
In light of the above, I must discount a previous account in this investigation that says the pool looked the same in the 1930’s as it does now.
Another important bit of information that John came up with is that there were no planks lying around the pool in 1954 — the planks seem to have been a modern addition.

I took some measurements and produced a drawing to give you an idea of scale. arch sizes  

25 June 2011 — New photos inside Arch still inconclusive

About a week ago, I cleared as much weed from the inside of the arch as I could — not easy when you’re working blind.
Yesterday I tested my new makeshift underwater light with two car headlight bulbs and a lead acid battery. My new light proved ineffective at penetrating the gloom behind the arch and not as effective as the small on-camera flash which unfortunately makes tiny particles in front of the lens look like floating dinner plates.

views inside arch

There is still weed to be cleared but I can tell by counting bricks that the chamber behind the arch is at least 1.4 metres deep. The width is the same as the arch at just under 2 metres. The height is unknown but the weed seems to be growing down from above the arch and during my recent clearing operation, I managed to push a stick up vertically behind the top of the arch to a distance of 1 metre — at least, I think that’s what was happening.

left pipe   right pipe

two pipessingle clay pipeI did manage to get some better images of the 5 inch pipes and the small iron pipe around 1 inch in diameter.

The two 5 inch pipes above the arch were the first to be found in the early stages. Note how the photo of the left pipe has caught a black circular shape that looks like it has entered a void — the chamber behind the Arch ? — mmm . . . could be the end of the cattle trough theory.

I am assuming these pipes are ceramic/clay but I must remember to take a magnet up some day to check if they are iron.

The clay pipe on the opposite side from the arch is about the same depth but has a much rougher look to the workmanship. The spigot end was not flush with the brickwork and protruded at a slightly awkward angle. It was not at right angles to the tangent of the circumference — it was squint!

iron pipeThe small iron pipe is at a similar depth to the Arch. A line from the centre of the Arch, through the iron pipe, lines up with the man hole at eleven metres from the edge of the Pool.

The next step is still to get a better understanding of the chamber behind the Arch. I don’t yet know if I have an arched tunnel heading for Quarter Colliery.
If the back wall of the chamber has a large pipe of 8 or 10 inches diameter, then the water tank theory could be getting a dusting off. If the chamber has no openings (other than up) then the charcoal kiln theory could be getting another look.

Clearing the weed with such awkward access will take some imagination. I can confirm that the visual distortion caused by looking through water means that what you see is not actually what you get and working with poles at 5 metres plus in deep water gives a very poor feedback of what is happening at the business end.

It’s unlikely that I will be doing any underwater industrial archaeology for the next two months as I am fully committed over the summer. So as they say in the good ol' U S of A — Happy Holidays.
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15 October 2011 — Behind the Arch

I was fairly sure I had cleared most of the weed from the arch by the time I lowered the camera into the pool last Sunday. Clarity of the water was excellent.
Previous still photos had been pot luck as I was working blind. This time I used the same underwater camera but in VIDEO mode — hopefully I would get a few useful frames, albeit at much lower resolution than the Still-photos.
New lights were attached but once again proved woefully inadequate. After the shoot, I viewed the video on the camera screen and the back wall of the chamber was just black.

I loaded the video into the computer and boosted the dark shadows. Although this dropped the quality, the resultant video is very informative.
From the Pool, I pointed the camera through the Arch (the First Arch) and saw the rectangular chamber of three vertical brick walls — I am assuming that the fourth (unseen) wall is the curve of the Pool. The width of the chamber is the same as the First Arch at just under two metres. The height of the chamber is greater than the Arch and I suspect this chamber may well be a maintenance/Inspection chamber with a manhole cover not far below the heather and grass.
The back wall of the chamber has another brick Arch (the Second Arch). It is the same width as the First Arch but appears taller. This may be an illusion or it could be that we are not seeing the bottom of the First Arch because of debris. The depth of the chamber between the First and Second Arches appears to be about three metres.
About one metre behind the Second Arch, appears to be another Arch (the Third Arch ?) and that has me a bit puzzled. The black void in the centre could well be a tunnel.


The next stage is to use the same camera in VIDEO mode with better lights. I have to devise a way to get the camera through the First Arch without touching the sides or bottom — you can see the resultant hailstorm of debris caused by this in the video. I would also like to move the camera through the Second Arch and also to turn it vertical and look up to the top of the ‘maintenance chamber.’

This new information should help focus the endless possibilities that exist at the moment. My money is currently still on an Airshaft and Air Tunnel for Quarter Colliery because that’s the direction the Arches are heading.

As for the two 5 inch pipes above the First Arch — if they only go through the wall of the Pool and stop at the chamber then my first guess is that they could have housed pressure instruments to measure the pressure inside the vertical chimney. Two identical instruments would have provided redundancy and more confidence in the reading.
I will be back at the Pool when I can but I am dealing with a few health issues at the moment.

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27 October 2011 — Mining Consultant Assesment

A big thanks to Miles Moulding for his OK to reproduce his recent email below.
Miles gives a very confident, convincing and detailed explanation of the original purpose of the Torwood Blue Water Pool.

My name is Miles Moulding and I work underground in disused mines (mostly as a consultant and or guide) and I’ve been a mining enthusiast for many years.
I can say with certainty what your blue pool is, I recognised it instantly.

Warren Moor Airshaft


Warren moor Ironstone Mine Downcast Shaft
on Kildale Moor, North York Moors.
(Opens in new window)
May 2007 (Public)

Flooded downcast shaft - the water level in this shaft is considerably higher than that in the upcast shaft so there is no longer any connection between them.

Photo by Jimbo




Yes, it’s a colliery airshaft. It’s a special dog-leg type, typically used where the shaft comes to surface well away from the main working surface site in an area that is not secured and/or remote.
What you do is you have the main shaft (vertical, almost certainly) come up directly from the mine to extremely near the surface, typically just a few yards short.
You then dig  a very short shaft just to the side of the main one, from the surface to maybe 4 yards or 6 yards deep. The two get connected with a tunnel.

Why do it this way? Because the miners didn’t want rocks and rubbish thrown down the air shaft into the mine from kids messing about at the top of the shaft. That’s why it’s offset, or “dog-legged”.
Quite a few here in Wales done the same way. Only used for vent shafts, not haulage shafts or similar, as the dog-leg poses no problem for air flow.
No need to do it that way on the mine site, as the site will have security. But in the woods in the middle of nowhere, a vent shaft would likely be done that way, it’s not a huge amount of extra effort and it means if people hurl things down it collects in the small shaft/chamber and doesn’t rattle down to the mine and pose a risk to men/machines below.
Railway tunnel vent shafts (or piston relief shafts) where the shaft is directly above the rails, will almost always be dog-legged in exactly the same way for the same reason. Right at the top.

The top of the shaft though should have a circular wall around it maybe 7 feet high.
The bricks have probably been stolen or the wall has been vandalised and pushed into the pool. The shaft shouldn’t be open like that, you should just see what looks like a short stumpy chimney to stop people falling in (or driving cars down!).
The fact that it’s a mile from the mine’s main shafts is neither here nor there, that’s nothing for a Victorian colliery. It could have over 100 miles of tunnel belonging to it, emanating out up to 30 miles from the main shafts in some cases.


I can also tell you the main shaft has suffered a significant collapse since the colliery closed, and I’ll reckon the collapse is right at the bottom in the actual seams where it joins the mine. It’s quite comprehensively blocked, because that water is separate from the mine’s main flood water. If it wasn’t, either the water level would be well down the main shaft (hence just a hole, no blue-pool), which would happen if the main shaft collar was at a lower altitude than the air shaft, or if the air shaft was the lower, then the entire mine would be draining from that air shaft.
That’s not the case, as it would be pouring out constantly, loaded with orange ochre and generally nasty.
Yes the shaft has flooded, as it would, but the flow is minimal, hence the clarity. It is now isolated from the mine, like I said, via a blockage that’s likely to be at the bottom.

So if you swim through that tunnel and those nice brick arches (typical of collieries), you should find a shaft dropping down to goodness knows what depth, could be anything from a few hundred feet to half a mile or more to the colliery below.
In the winter I expect you’ll find the water in the deeper parts strangely warm. Warm water from in the main shaft will be rising up, and the cold water from the pool surface sinking down and getting heated up by the walls of the main air shaft (which will be around 11 degrees C, even if it’s -10 on the surface. If that small pool didn’t connect to a much deeper shaft, it wouldn’t do that.

You would normally (but not always) have a thick heavy cap or lid on the ground directly above the main shaft (so a little way from the small surface shaft). The purpose of this is to provide an easy means of inspecting the main shaft. You lift the lid (built heavy enough to require a winch or hoist to stop casual trouble makers trying it) and it opens directly down to the main shaft. You can lower a man down on a trailer-mounted powered winch to inspect it, and haul him back up when he’s finished. This lid, if it has one (and it might well not), will probably be buried in undergrowth and very hard to find now.

Would be a nice weekend project to just empty it and go for a look. Just hire a small petrol pump for a weekend from your local hire shop and camp there with it, any respectable pump should empty that chamber very quickly. The water is clean. Then drop an extension ladder down and have an explore down the tunnel (but don’t fall into the main shaft at the end!). If the pumps pipe will reach you could drop the main shaft water by 20’ or so to get a picture of it.

Please disregard comments that it might have had a Cornish beam engine on the site. It had nothing of the sort, no engine or fan or anything. It’s not an escape road, it’s highly unlikely that it was ever laddered. It’s just a vent shaft.
I’m very confident in my identification (I’m not guessing), I’ll be very surprised if any of the above is inaccurate. If it was in my neck of the woods I’d just push a diver in if I wanted to confirm it, but I’m sufficiently sure here I doubt I’d bother.

The top of the airshaft/chimney wouldn’t have had a beehive roof, just a round wall like a short chimney, maybe 6’ to 8’ high, acting like a safety barrier.
The 1” pipe probably isn’t a pipe but a more likely a scaffold support peg (which could be a length of scrap pipe from the colliery). In all mine shafts you find short steel pegs sticking out from the walls, left over from the shaft’s creation and brick-lining, rarely removed afterwards. Looks like it’s a bit of scrap air-line pipe to me.
The 5” pipes look only just below the ground level? perhaps they were just above ground level when the shaft was made. In truth I’m not sure of their purpose. Mind you I often abseil down shafts of all types, there are pipes and things everywhere, their purpose is obvious about half the time and the rest are a mystery!
As for whether someone tried to convert it into a swimming pool in later years – I can’t comment on that, would explain why the wall was taken down. The water will be warmer (in winter) than an isolated pool would be, but you wouldn’t catch me bathing in it. I can’t comment on whether if someone did try to use it as a pool, whether they attempted to roof it or not. I’ve never heard of anyone using the top of a flooded shaft as a swimming pool, but it’s feasible I suppose.
You say the collar is 20 feet diameter? That’s quite a generous bore, I doubt the main shaft will be that wide, probably 10 feet.
I hope this has been of use!

What's Next ?

My next job is to get some decent quality video inside the second arch and see the first few feet of the vertical shaft dropping down over 800 feet — makes me shudder to think what might have disappeared down there already.
For the time being at least, I have to say that NOBODY SHOULD SWIM in the Torwood Blue Water Pool.

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Nigel Greetings from Nigel Turnbull

This same Guestbook appears on both pages of the investigation

If you have knowledge of any of the above or you know someone who does, please get in touch.

Your comments please . . .

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