A to Z: a multiplicity of Ms

M

MAGNETITE

As mentioned previously, in the 1850s a seam of iron rich ironstone was discovered in Rosedale. Also known as lodestone, magnetite had long been a valued mineral because of the amount of iron ore it contains, so much so that it is often magnetic.

Rosedale - copyright Colin Dilcock, NYMNPA

The discovery in Rosedale led to the rapid development and expansion of the mining and calcining industry there and in the wider area. There were great expectations …

“Professor Phillips delighted and informed the company by his description of the ‘Ironstones of Cleveland’ … The Rosedale band at its richest points, yielded 50 per cent [ore] and in many places 42 per cent. The Rosedale stone was magnetic and contained phosphorous, it was not merely magnetic, but it had an inherent magnetic polarity … There must spring up over the Cleveland district, through the working of the iron ore, great towns, with a numerous and active population; and, as a result, the moorland would be brought under cultivation and this once dismal tract of 20 square miles would rejoice in all the material means that could promote human happiness and prosperity…”

From a meeting of the British Association for the Advancement of Science at Leeds, as reported in the Manchester Courier and Lancashire General Advertiser, 2 October 1858.

However the actual magnetite seam was soon exhausted leaving the industry exploiting poorer ironstone and slowly declining into the 20th century. The magnetite proved to be rather a flash in the pan.

This Exploited Land of Iron logos

MESOTROPHIC LAKES

There are very few natural lakes in the North York Moors due to geology and climate, which makes Lake Gormire on the south western edge of the National Park even more remarkable. In the last Ice Age a hollow was formed by a meltwater channel between the edge of the moving Vale of York ice sheet and the edge of the North York Moors gritstone escarpment. The channel damned up and the lake left behind divided into two bodies of water – Gormire and the much smaller, Buttermere.

These are mesotrophic lakes – containing a narrow range of nutrients in medium concentrations. This type of lake chemistry is rare and becoming rarer as lakes are effected by artificially increased levels of nitrogen and phosphorus and so become eutrophic. Lake Gormire is surrounded mainly by semi natural woodland and fed by springs and so largely circumvents the risks of artificial diffuse pollution and nutrient enrichment.

Because of their chemistry Mesotrophic lakes can support higher levels of diversity of macrophytes (algae), aquatic plants, invertebrates and fish. The fen (‘mire’, ‘mere’) plants around Gormire/Buttermere reflect the acid soil, so there is Marsh cinquefoil Potentilla palustris, Common skullcap Scutellaria galericulata and Tufted loosestrife Lysimachia thyrsiflora, as well as Bog bean Menyanthes trifoliata and Water horsetail Equisetum fluviatile. Gormire is particularly popular with noisy water birds, mating toads and freshwater leeches, all exaggerating the primeval sense inside this Ice Age hollow.

Lake Gormire from Cleveland Way, north of Sutton Bank - copyright Mike Kipling, NYMNPA

Lake Gormire and the area around it is a designated Site of Special Scientific Interest. The cliff slope woodland above Lake Gormire is the Garbutt Wood Nature Reserve managed by the Yorkshire Wildlife Trust.

MILKY WAY

The Milky Way is a galaxy of billions of stars and planets sometimes partly visible to the naked eye as a milky looking band of light in the night sky.

Milky Way and Perseid Meteor Shower Sutton Bank - copyright Russ Norman Photography.

We’re in the middle of the Dark Skies Festival 2017 here in the North York Moors National Park. The dark skies over National Parks make it easier to see the lights of the galaxies around us. This February is particularly good for viewing Orion and also a very bright Venus.

February 27 1920   The mysterious stars

…Later in the evening a half-moon shone in a filmy sky across which, from S.E. to N.W., ran a Noë-ship of thin white clouds. A soft mist hung in the far valleys, but the nearer moory slopes loomed clearer. In the pastures the furze bushes were startlingly like huge black beasts grazing on the rimmed herbage. No sounds broke the utter silence of the moonlit hills; the wind had almost died away, but as I stepped over the little rill from Thunderbush Farm [Commondale], I heard its faint, musical ripple.

The ever-mysterious stars flashed through the interspaces of the filmy clouds and circled silently above the dim earth. Sirius flashed due south whilst mighty Orion hung high above the moor edge, his glory somewhat dimmed by the moon. What would life have been without the stars?”

A Man of the Moors: Extracts of the Diaries and Letter of Frank Elgee.

MINI-BEASTS

We use the term mini-beasts for the tiny invertebrates that go without notice until they’re looked at under the microscope and a menagerie of marvel and dread is revealed.

Identifying and counting river invertebrates is a very useful way of assessing the health of a river at a particular spot. Certain species indicate good water quality and others, poor water quality; a change in species/numbers indicate a change in water quality e.g. a pollution incident. There is a national programme of riverfly monitoring led by the Riverfly Partnership. Results are recorded centrally and indications of a potential incidents are reported to the Environment Agency. The National Park run a number of local Riverfly Monitoring Workshops for volunteers – the next one is 1 March.

MOSCHATEL Adoxa Moschatellina

Moschatel is a perennial unobtrusive plant which likes the damp, shady conditions found along woodland edges and on shaded hedge banks. It flowers between March and May, producing five lime green flowers on top of a leafless stalk, four flowers face outwards and one flower faces upwards, forming a cubic which has led to the plant’s other common name – Townhall Clock. The plant grows along the ground through rhizomes with the flower stalks growing up through its leaves to only c. 15cm tall. It is a common plant but easy to miss – look out for it in early spring before it gets hidden by taller plants.

Moschatel at Sieve Dale. Copyright Ami Walker, NYMNPA.

MOTTE AND BAILEY

Historic England suggest there are over 600 motte castles or motte-and-bailey castles in England. These were early medieval fortifications built by the Normans and made up of a large mound of earth/rubble (the ‘motte’) with a defensive palisade and tower on top, and an embanked enclosure with other buildings (the ‘bailey’) adjoining.

A motte and bailey castle could act as a fort when required as well as providing the residence for the local landowner/representative of the King and a centre for feudal power. They were often built on high ground to take advantage of the extra height to dominate the landscape and overlook access routes.

Soon after the beginning of Norman rule in England came the ‘harrying of the north’ – a military campaign to overcome and overwhelm the population in the north of the country and hammer home the idea that the Normans were here to stay. The new motte and bailey castles were a highly visible tool for holding that ground and reinforcing that message.

By the 13th century castle design had moved beyond the basic motte and bailey. Although the timber structures have largely gone, the earthworks are often still traceable in the landscape, and rubble mottes and the remnants of stone towers remain. Many are scheduled. Examples in the North York Moors include Hood Hill, Easby motte, and Foss Castle.

MOTHS

Moths are often considered the poor cousins of butterflies in the Lepidoptera family. The most obvious difference between butterflies and moths are that the former are active during the day whereas moths are mostly (but not all) nocturnal, feeding on the nectar of night blooming/night scented plants. Another difference is that when resting, butterflies usually close their wings whereas moths leave theirs open and this makes it easier to examine their intricate patterning and refined colouring. But as with most ecological questions – what is the difference between butterflies and moths? – there is no obvious answer and always an exception. Moths can be just as colourful, just as beguiling and just as in peril, as butterflies. For more on moth conservation see here.

Shandy Hall, Coxwold has become a location for moth study and reporting over the last few years. The gardens there provide a semi-natural/cultivated habitat for many species – over 400 different species have been recorded in the gardens to date.

Previously on the North York Moors A to Z … A, B, C, D, E, F, G, H, I, J, K, L

Ageing Mussels

Simon Hirst – River Esk Project Officer

As mentioned previously, the River Esk in the North York Moors is the only river in Yorkshire with a Freshwater pearl mussel population Margaritifera margaritifera. The population is estimated to be comprised of approximately 1,000 individuals and is in drastic decline, so much so that it is on the verge of extinction. The decline is due to a number of linked causes such as water pollution, choking of the river bed by sediment build-up, deterioration in fish numbers and habitat degradation.

A dense bed of healthy adult mussels in Scotland. Copyright Sue Scott - SNH,

We’re working to improve the riparian habitat and so help secure the local population of Freshwater pearl mussel in the River Esk. We recently sent a sample of mussel shells from the Esk* over to the Swedish Natural History Museum in Stockholm, in order to determine the age of the mussels in the River Esk. The maximum age of Freshwater pearl mussels in the wild has been shown to vary considerably, from a low of 35 years in Spain (warmer, lower latitude rivers) to over 200 years in arctic areas (colder and high latitude rivers). Information from the ageing study would tell us how long we have left to save the Esk population from extinction and help identify the approximate time when the River Esk mussel population went into decline.

Dr Elena Dunca from the Swedish Natural History Museum sectioned (cut though) the shells supplied and then counted the growth lines on the mussel shell using a high powered microscope.

1

Growth lines visible on the freshwater pearl mussel shell.

Esk FWPM - Age and length graph - Swedish Natural History Museum

This age/length graph will allow us to age fairly accurately any mussels we find in the wild in the future just by measuring them.

A total of 10 shells were aged by Dr Dunca, and the graph below shows that the mussels sent to Sweden ranged in age from 45 to 88 years of age.  The mussels in the River Esk also showed normal growth rates.

Esk FWPM - Length frequency graph - Swedish Natural History Museum

Length frequency graph of mussels in the River Esk

The smallest live mussel we have found in the Esk up to now was 75mm (approximately 28 years of age). This means the last time the Esk mussels reproduced successfully in the wild was in the late 1980s. The largest mussel we have found in the Esk was 156mm (approximately 100 years of age), which means it was born around the time of the First World War. The vast majority of the mussels are around the 130mm-140mm size range (approximately 80 years of age). We now know for scientific certainty that the Esk has an ageing population in need of help!

The best hope for our mussels is for them to start to successfully reproduce again. We’re working with the Freshwater Biological Association (FBA) who are carrying out captive breeding work in the Lake District. We hope to re-introduce the captive bred young Esk mussels from the FBA Facility back into the Esk once the riparian habitat is restored enough to sustain them, and so ultimately stop this species from becoming extinct in the wild (of Yorkshire).

* Please note – No mussels were harmed in the making of this study! We used empty shells that were found on the banks of the Esk.

Thanks to our funders at Biffa Award, for their support to carry out this vital research work.

Biffa

Biffa Award is a multi-million pound fund that helps to build communities and transform lives through awarding grants to community and environmental projects across the UK, as part of the Landfill Communities Fund.

Revitalising the Rye

Tom Stephenson, External Funding Officer

There must be something in the water in the North York Moors, having just started delivering the This Exploited Land of Iron Landscape Partnership Scheme, the National Park Authority and its partners* have also been successful at the first stage of securing a further £2 million of Heritage Lottery Fund money to develop our next Landscape Partnership SchemeRyevitalise.

The River Rye and its tributaries rise on the moorland of the North York Moors, flowing through fast and clear upland becks that carve out steep sided dales until the land flattens and the river slows and broadens taking on the character of the undulating Howardian Hills and the flat lowlands of the Vale of Pickering. The Ryevitalise Landscape Partnership Scheme under development will help appreciate and enhance the Rye’s verdant landscape and clear waters which have been prized for millennia for their beauty and tranquillity resulting in a more natural, better functioning and better understood landscape.

Planned projects will cover four themes:

  • Water Environment, looking at aquatic habitats of the Rye and rare and threatened species;
  • Water Quality, working with land-owners and managers to reduce pollution;
  • Water Level Management, working alongside our delivery partners to harness natural processes to manage the sources and pathways of flood waters; and
  • Reconnecting People, improving the understanding of the river landscape by telling the story of its evolution and helping people to protect their heritage.

Without wanting to spoil the surprise of future blog posts, below are just some of the particular issues we are aiming to address through Ryevitalise scheme projects if we’re lucky enough to be successful in our Stage 2 application due in October 2018.

The wet…

Water is the major theme of Ryevitalise. Through the Ryevitalise scheme, from the high moorlands to the lowland wetlands, we will identify priority areas of riparian habitat for restoration to ensure existing high-value habitats (and their species) are in positive management and can act as nodes from which to extend outwards by creating ‘stepping stones’ and connections between these habitat sites.

Wetter still, we will assess the geomorphology and key features of the aquatic environment and target areas where aquatic habitats could be improved by creating changes to the channel through creating gravel bars, by placing debris to create slacks or by making changes to river bank profile. This work will include a survey of the habitats and species of the oxbow lakes in the lower Rye, and also the collecting and analysis of sediment cores to look for valuable paleoecological data which might shed light on how the local landscape formed.

The dry…

We have previously reported on the problems that fluctuating water levels in the River Rye
in Duncombe Park has on the White-clawed crayfish, the only native crayfish in the UK, White-clawed crayfish - during 2016 rescue in Duncombe Park. Copyright NYMNPA.which is suffering from a “perfect storm” of threats. Ryevitalise will prioritise protective measures for the existing population and carry out a feasibility study to identify where potential local ark sites might be located. Ark sites for White-clawed crayfish would allow populations to become established in isolation, separated from the threat of non-native crayfish and the crayfish plague they can carry.

The small…

Alcathoe bat. Copyright Cyril Schonbachler.One of the Rye catchment’s smallest inhabitants is the Alcathoe bat. Relatively new to science, having been first identified in 2001 and only recently becoming the latest addition to the UK bat family, this little creature has only been found at two other sites in the UK so far. Ryevitalise will seek to establish a deeper knowledge of where colonies of the Alcathoe bat and other key bat populations are, along with the requirements to support their survival.

The tall…

At the other end of the size spectrum and intrinsically linked to bats are some of the Rye catchment’s largest residents – its ancient and veteran trees. The area is a national hotspot for these giants that not only give an air of majesty to the landscape as living witnesses to history but also provide important habitat for many invertebrate species as well as providing important roosting sites for Rye bat populations.

The old…

Not only is the Rye catchment home to iconic built heritage like Rievaulx Abbey, Rievaulx Terrace, Duncombe Park and Nunnington Hall but it also contains a wealth of less obvious heritage that traces vernacular land use and tells the story of the working River Rye. Working with local history groups, Ryevitalise will record the remaining evidence of man’s relationship with the river over the centuries, surveying and recording the traces of the former agricultural and industrial settlements along the river banks. Accurate 3D models will be produced of the principal remaining watermills, iron working sites, water races and leats. Essential conservation and consolidation work will be identified from the surveys carried out.

The new…

Meanders in Rye near Sproxton - can see the water crowfoot beds within the river, September 2016. Copyright North East Yorkshire Ecological Data Centre.Like a lot of watercourses, it is not practical to access the river in its entirety at ground level. So as part of the Ryevitalise scheme an Unmanned Aerial Vehicle flight will record the entire 50km main river from its moorland origins all the way downstream to where it
meets the River Derwent. This will produce an invaluable record and will provide an insightful journey along the river for local communities, highlighting how this vital artery connects them all. Tailored sections of flight data will be made freely available to local schools, businesses, and community groups as a community resource; it will also form part of the scheme’s wider education programme.

We are all really excited about the next steps in developing the Ryevitalise scheme; the opportunity to make the most of the wealth of habitats, species and history surrounding the river; the potential to make a lasting difference to this wonderful landscape, and the chance to create a real splash.

HLFNL_2747

* Partners currently include East Yorkshire Rivers Trust, English Heritage, Environment Agency, Forestry Commission, Howardian Hills AONB, National Trust, Natural England, North Yorkshire County Council, Ryedale District Council, Woodland Trust, Yorkshire Wildlife Trust, as well as local communities.

Last year’s top 5 posts

Whether by accident or design these were our top 5 posts in 2016, according to the number of views.

Woodland to be thinned - copyright NYMNPA

1.The aesthetics of trees

If you’re a land manager and you’re interested in grant to help you create, manage or improve your own woodland masterpiece – here’s a link to the national funding that’s available. Watch out for the set application windows because they’re often quite short.

The current adaptation of The Crown, Helmsley - copyright NYMNPA.

2.Historic Pub Culture

As part of the renovation of The Crown Hotel in Helmsley the building was subject to a re-assessment of the development of its historic fabric by Colin Briden, an Historic Buildings Archaeologist who reported in April 2016. His report concluded…

Although partly demolished in the 18th century to bring it ‘up to date’, and extensively refurbished in the 20th century to make it look ‘olde worlde’, the building retains considerable evidence for a high-status late mediaeval timber framed house of two jettied storeys (where upper storeys project beyond the lower storey) and attics in a prominent position. The house is of an unusually large scale. Other comparable size houses in the wider area are from much later dates.

Now that the building is free from the unfortunate results of the 20th century remodelling it is possible to see it as it really is – ‘the battered remnant of late mediaeval construction work on the grand scale carried out by an unusually wealthy owner’.

In 1478 Helmsley was sold to Richard, Duke of Gloucester, later Richard III; it reverted to the de Roos family on his death. The name of the subsequent hotel is suggestive of a reference to this short lived but significant royal ownership.

In its latest adaptation, the building is now a shop.

capture

3.Face to face with the past

Raven - the Watcher by JestePhotography. http://jestephotography.deviantart.com/art/Raven-The-Watcher-532656250.

4.A ‘Gothic’ icon

Historic England survey of earthworks at Stoupe Brow alum works - copyright Historic England

5.Cliff edge archaeology

Following our work in 2014-15 (reported in early 2016), we were pleased that Historic England were able to remove one of the coastal alum working Scheduled Monuments from the Heritage at Risk register because we had fully recorded those parts of the monument which were under threat. However, four other Scheduled alum working sites remain on Historic England’s Heritage at Risk Register despite our efforts to record some of their most vulnerable features. So what next?

Working with Whitby Museum and specialists from Historic England, we held a seminar last spring bringing together a group of dedicated people with a strong interest or connection to the coastal alum working sites – landowners, archaeologists, academics and private researchers – to review what we know about the alum industry, to decide what we don’t understand and to look for a way forward to manage the risk to the sites under threat and ensure that we do not lose the valuable information held within them. One of the ideas emerging from the seminar was a further excavation project with an emphasis on engagement and interpretation as well as research.

Archaeological excavations take considerable planning and funds to ensure that they are carried out to a high standard and achieve objectives without causing accidental damage, so it can be a slow process getting started. We are now working towards setting up a project to investigate one of the sites which we didn’t include in the investigations in 2014-15 – the alum works at Stoupe Brow, near Ravenscar. An extensive system of reservoirs and water leats (dug channels) was revealed on the nearby Fylingdales Moor after the 2003 wildfire and we know that this water management system supplied the needs of the alum processing at Stoupe Brow, but other than that we currently know very little about this site. Historic England recently completed a topographic survey of the earthworks so we can now see how the site was laid out, but not how it operated. The site still includes its alum house (where the final processing to produce alum crystals was carried out) and there is still a general gap in knowledge when it comes to how alum houses functioned. As well as trying to discover more about the practical operations at the site the project will record the structures which are currently being gradually lost over the cliff edge. A big advantage of this particular site is that it is more accessible and less dangerous compared to some of the other coastal alum working sites – providing great opportunities for volunteers and visitors.

The first stage of the project is producing a project proposal which will outline what we want to do and how much it will cost, and this is expected by the end of this winter. The next step will be using the proposal to generate partnership support and seek funding. It is early days yet, but we hope this will develop into an exciting project – watch out for further posts as our plans progress.

Mags Waughman, Monument Management Scheme Officer

Cosy and warm

John Beech – Land Management Adviser

Hygge (pronounced hoo–gah) has been a major trend for this Christmas period. It’s a Danish ‘concept’ of living cosily e.g. wearing thick socks whilst drinking hot chocolate and watching Murder She Wrote – which can make us feel better about the icy and harsh season outside.

For a number of wild animal species, they have their own version of hygge except for them it’s a necessary survival mechanism. Hibernation is an extended period of deep sleep, or torpor*, which allows animals to survive the winter extremes. By reducing their metabolic rate and lowering body temperature this enables them to sit tight, conserve their energy and survive through the cold periods when food is scarce or has little energy value. *Animals in a state of torpor rather than sleep can venture out to try and find additional supplies during warmer winter spells.

In autumn as the temperature begins to fall and the nights draw in, many of the small mammals that live in our fields, woodlands and hedgerows forage for extra food to store over the winter and look for a suitable site (a hibernaculum) to hole up in for the coldest part of the year. Autumn months are often one of the better times of year to see small mammals in the North York Moors such as mice, voles, shrews and Hedgehogs (Erinaceus europaeus) out and about eating vast quantities of food to build up fat reserves which will carry them through to the spring.  Following this period of feasting they retreat to somewhere suitably warm and undisturbed and begin to enter into a period of hibernation, which can last for up to four months of the year depending on the harshness of the weather. Also in autumn bats relocate to hibernation roosts looking for a constant temperature and to avoid frosts and freezing e.g. caves, trees and built structures.

And it’s not just our small mammals that hibernate:  Queen bees dig in for the winter and also some species of moths and butterflies, like the Duke of Burgundy (Hamearis lucina) which hunker down in grassy tussocks. Many of our reptiles and amphibians also hibernate. Adders find warmer crevices under boulders or in dry stone walls. Newt species spend the winter in the muddy banks of ponds, under paving slabs, piles of wood or in a handy compost heap. Common Toads (Bufo bufo) sleep out the winter buried deep in damp places such as leaf piles or compost heaps, before emerging to travel back to their traditional breeding sites in early spring. The Common Frog (Rana temporaria) which needs to keep damp is able to partially freeze in its state of hibernation before thawing out in spring. Occasionally such species come out of hibernation during any short sunny spells in the winter to make the most of the weak sunshine, only to return to their hiding place when the temperature falls again.

Malkin Bower, Bilsdale - in winter - copyright NYMNPA.

So as you’re reading this, hopefully somewhere cosy and warm, spare a thought for our wildlife that’s out there sleeping through the winter, hidden away from view deep in their retreats, practising their own life saving hygge and waiting for the first signs of spring.

Sounding like Christmas

Clair Shields – Planning Policy Officer/Building Conservation Officer

Now that the lights are twinkling and the decorations are up, everywhere you look it is all about Christmas. So with this thought in mind I was intrigued as to what festive sounding names the built environment can offer at this time of year. Below are a few Christmassy sounding historic features found around the North York Moors

Christmas Tree Field, Jingleby – This is a double hit of a Christmas sounding site within Dalby Forest. The archaeology of the wider area is significant and complex. The area includes Bronze Age round barrows, and a number of embanked pit alignments (prehistoric linear boundary earthworks) as well as later banked field boundaries which might be connected with rabbit warrening. There is also documentary record of a Jenglebee Cross but its exact location isn’t known.

Goose I’ Th’ Nest is one of a row of nine boundary stones on Wheeldale Moor, described as a natural boulder or deeply buried slab with letters ‘PCE’ and an illegible date.  Good Goose Thorn is another boundary stone, possibly of medieval origin, located on the parish boundary between Loftus and Glaisdale. Its specific name is recorded on the
Example of a boundary stone on the North York Moors.1st edition 6 inch Ordnance Survey Map of 1853

Although these particular boundary stones are not Listed or Scheduled, there are many that are. Boundary stones identify the start of a land boundary or the change in a boundary, especially a change in direction, and are a feature of the North York Moors. They are often marked on the most relevant face with the landowner’s or parish initials to indicate the ownership. Like waymarker stones they would have been important features for people having to cross the moors, defining the route to follow in a landscape which has very few points of reference.

There are a number of features called Stocking – Stocking Craggs, Stocking Dike,
Stocking House, WesterdaleStocking Lane and Stocking Hill. There are a couple of Stocking Houses – this Stocking House, to the north-west of Westerdale, is a group of unlisted buildings. Although not listed, together these buildings are typical of a traditional North York Moors moorland farmstead – small in scale, linear in form and of stone and pantile construction.

Frost Hall in Farndale is a farmstead with a range of listed farm buildings and a listed
farmhouse dated 1826. The range includes a threshing barn with a horse engine house Frost Hall, Farndale(for horse powered machinery) attached to the rear. Close by the farmstead there are a number of staddle stones (arranged to lift structures like granaries or haystacks off the ground), the remains of a saw pit (in which to operate a two handed vertical saw for timber) and also a chambered sheep fold which has been used to hold bee hives.

Holly Cottage, Holly Lodge, Holly House – there are plenty of Listed Buildings with this name, presumably there had been a holly tree nearby or otherwise the name sometimes
derives from the word ‘holy’. This one is Holly Cottage in Lythe, a characterful Grade II
eighteenth century house. This building is a good example of how a building has evolved Holly Cottage, Lytheover the years – probably originally a traditional longhouse it has clearly been raised at some point in its history and also extended. The variation in windows style, sizes and their location on this elevation all add to its unique character and adds to its special interest and architectural character and is typical example of the North York Moors vernacular.

Winter landscape: coming over the top. Copyright - David Renwick, NYMNPA.

Merry Christmas and a Happy New Year from the North York Moors National Park

A scientific perspective

Aside

Natural England‘s Chief Scientist visited the North York Moors last week to see the ongoing work in the River Esk catchment to help save our dwindling population of Freshwater Pearl Mussels.

You can read about why he came and what he thought here.

 

End of an era

Our Senior Archaeologist is taking phased retirement, so before he goes he has been asked to reflect on his time with the North York Moors National Park.

Graham Lee – Senior Archaeological Conservation Officer

graham-leeHow do I sum up a career lasting over a quarter of a century in a few paragraphs? It is a strange feeling to have 26 years seemingly flash by so fast.

I started work for the North York Moors National Park in April 1990, having previously worked in the archaeology section of North Yorkshire County Council since the summer of 1983. I had decided many years before that I loved the north of England and had no desire to return to my southern ‘roots’.

Graham had decided many years before that he loved the north of England, whatever the weather ... Copyright - NYMNPA.One of my first tasks with the National Park was the completion of a management survey of one of our large estates, encompassing moorland and large blocks of forestry. This quickly whetted my appetite for the excitement of making new archaeological discoveries – often very subtle earthworks, no more than a handful of centimetres in depth or relief – despite an exceptional tradition of previous high quality archaeological fieldwork in the region. Working solo in large blocks of conifers was a good test of dedication – crawling under the branches of dense stands of conifers searching for vague earthworks mapped in the 1890s – and the steadiness of nerve, when yet another wretched pheasant exploded out of the leafy vegetation where I was just about to step! In recent years the delights of discovery have been broadening thanks to new technology and techniques, especially LiDAR which provides an aerial view through tree and ground-cover vegetation of archaeological remains that were previously hidden or obscured.

If you have a passion for the past, the North York Moors have something for pretty much everyone – enigmatic Neolithic rock art; surviving prehistoric pitted boundaries and avenues; upstanding Bronze Age funerary monuments and field systems; Roman encampments; medieval castles and monasteries…

Human industry is also well represented – from the earliest iron industry through the search for alum into the full-blown “iron rush” of the mid 19th century, the exploitation of coal and jet, and the plentiful local rivers managed to provide motive power for a range of watermills. Research and conservation priorities relating to these local industries finally led to our new HLF Landscape Partnership Scheme, This Exploited Land of Iron. Some 15 or so years in gestation, it is very rewarding to see new generations captured by the excitement of the important remains of our 19th century ironstone industry and the associated development of early railways – although the original scheme for a canal link between Whitby and Pickering would have been a sight to behold and a major tourist attraction if it had ever been built.

Into the 20th century, remains survive here from both world wars – in the form of coastal defences, army camps as well as troop training and target practice areas. Finds are still occasionally made of 2nd World War unexploded ordnance in former training areas across the North York Moors, in particular after the wildfire on Fylingdales Moor in 2003 which affected two square kilometres of heather moorland.

Fylingdales Moor after teh wildfire in 2003. Copyright - NYMNPA.

Although an environmental disaster – the severity of the fire in reducing the shallow peat cover to ash, this event was an archaeological revelation. Virtually everywhere you looked, subtle archaeological remains became visible, including the drip gulleys around former prehistoric round houses, low stony prehistoric boundaries and cairns, large numbers of previously unrecorded examples of Neolithic rock art and occasional shallow trenches which resembled grave cuts with a subsiding infill. As numbers of the latter quickly increased their interpretation became clear – slit trenches from 2nd World War troop training. I remember my first visit to the site after the fire when the ground was reddened and blackened, covered in ash and still smouldering; few trees had survived and many had toppled after the peat holding their roots in place had been burnt away. Flashes of colour were very noticeable, such as an adder emerging from its underground refuge having survived the conflagration. A major project ensued, both to protect and restore the moorland habitat and to record and investigate the breath-taking remains of surviving archaeology.

Rosedale Calcining Kilns in a perilous state. Copyright - NYMNPA.There have always been new specialisms to get to grips with. A visit to the Scheduled Rosedale iron calcining kilns with the Park’s Conservation Director at the time revealed that a portion of one of the kilns’ firebrick linings had collapsed the previous winter. This led to a major conservation project to stabilise these huge monuments which ran for three years in the mid 1990s, a forerunner of This Exploited Land which will continue the efforts to conserve these monumental sites 20 years on.

Conservation project to stabalise the Calcining Kilns in the 1990s. Copyright - NYMNPA.

It has been such a pleasure working with like-minded and dedicated professionals, both in my own National Park, but also with colleagues throughout the family of British National Parks, and Historic England and Natural England. We’ve shared experiences and ideas to the betterment of our discipline from research to management, and also shared the excitement of attempting to bring our subject, which we love, to life for anyone who cares to see and to get involved.

Graham at work - examining finds at an archaeological excavation - Coxwold Creative Minds Project, March 2006. Copyright - NYMNPA.

The National Park Authority is currently looking for a new Senior Archaeologist to lead on archaeology in the North York Moors. The closing date for applications is 26 January 2017.

Practical Chemistry

Aside

Following on from our last blog post about lime mortars and traditional buildings – there are a series of upcoming workshops over the next few months on using hot mixed and other traditional lime mortars, aimed at practitioners in the north of England.

Further information – lime-mortar-workshops-january-to-march-2017

The Chemistry of Buildings

Building Conservation Team

The Building Conservation team at the National Park have a vested interest in keeping the area’s traditional buildings in good repair so as to maintain and secure this particular element of the North York Moors’ special qualities. We have a new Advice Note on using lime mortars, the rudiments of which are explained below.

Most buildings in the North York Moors were traditionally constructed using stone and lime mortars (to bind the stonework together), often with earth and rubble filled cores. Lime was used for bedding and pointing the stonework and for rendering. Rendering with mortar was used to cover poorer-quality masonry underneath or to make a building more weather proof, for example on the coast. Most historic buildings were constructed from materials found locally and this contributes to what is distinctive about the ‘local vernacular’.

When it comes to repairing a surviving traditional building it is important to understand how they work. These buildings are usually of simple construction and built using breathable materials. Bricks and stone are bonded with flexible and permeable mortars made of lime and sand which allow the building to ‘breathe’. When it rains moisture is absorbed into the external surface but is then able to evaporate through the more porous pointing or render. Using a lime based mortar or render for repairs nowadays means that this process can continue.

In contrast modern cement mortars and renders along with plastic paints, waterproof sealants and damp-proof courses all act as barriers to a traditional wall’s natural ability to breathe. The trapping of moisture within permeable materials like stone can exacerbate the very problems these products are trying to resolve. The use of cement-based mortars can have a significant negative visual (photo below left) and physical impact on traditional historic buildings. The photo below (right) shows the extent of stone decay caused by the use of a cement mortar. Because the cement is much harder than the stone, moisture cannot evaporate through the joints and instead evaporates through the stone causing it to ‘weather away’ through premature erosion.

You can usually tell what type of mortar has been used most recently; cement based mortars tend to be dark grey and hard in appearance and texture whereas lime based mortars are generally lighter and softer in appearance and texture. Because they allow the surrounding masonry to dry out the colour of the stone will also lighten.

There are a number of different types of lime mortars/renders. Replacing like for like is important.

Non-hydraulic lime is the raw material produced when limestone (calcium carbonate) is fired, often called ‘quicklime’ (calcium oxide). It is sold in a slaked form (with water) as lime putty which is then mixed with an aggregate (e.g. sand) to produce mortars and plasters. These putty limes possess good breathability and flexibility and are ideal for use with soft porous materials allowing the maximum permeability.

Hydraulic lime comes in powdered form and will start to set as soon as it comes into contact with water. It is ideal for use in wet or very exposed situations or where there is a need for a higher compressive strength or a quick set. Hydraulic limes come in a variety of strengths e.g. NHL2, NHL3.5 and NHL5 – the higher the number the less flexibility and breathability the mortar will have.

Hydrated or bagged lime is a form of non-hydraulic lime which is sold as a powder. It is sold by builders’ merchants as an additive for cement mixes in order to give modern cement mixes more plasticity and workability. It is generally considered to be inferior to lime putty, not least because an unknown proportion will have reacted with carbon dioxide and set by the time it reaches the site.

Hot-mixed lime is made when quicklime is mixed with water and aggregate simultaneously. The vast majority of historic lime mortars were probably hot-mixed. There are several benefits of using a hot-lime mortar: it can produce cleaner work as there is less leaching, it has a easily-workable elasticity which produces solid and full joints, it appears to be more breathable and therefore more compatible with stonework, and it has potential for use in colder weather notwithstanding the requirement for protection from freezing during the curing (setting) process.

A standard pointing mix consists of a lime mortar mix of 1:2½ lime:sand (sand mix of 50% sharp sand and 50% builders sand) for a slightly recessed bagged finish. However there may be times when a bespoke mix is required such as when different colour sand is needed to match existing historic mortar.

Repointing is only needed where mortar has become loose, decayed or eroded to an extent that water has started to penetrate the joints. If the mortar is firm or so hard that it needs to be chiselled out then it is best to leave it in place as removal could damage the masonry. The repointing of delicate ashlar joints (made out of worked stone) is not generally advisable as the joints are so fine that getting old pointing out can lead to irreversible damage of the masonry.

If repointing is necessary joints should be carefully raked out manually or by non-electric tools (no angle grinders) to a depth equal to one and half times the width of the joint and never less than 35 mm. Great care must be taken to keep the edges of the stone intact and joints should never be widened. Work should not be carried out when there is a danger of frost or heavy rain (this is less important when using a hot lime mix). Mortar must be protected from drying out too quickly from wind, rain and frost by protecting the area. Rain must never be allowed to strike the mortar and stonework until the setting process is complete.

The mortar should be stippled as the initial set takes place, with a stiff bristle brush, to produce a textured appearance capable of shedding water and slightly set back from the stone outer surface to ensure the full arris (edge) of each stone shows clearly in relief.

The photo below (left) illustrates a good lime mortar mix and pointing method. The aggregate used in the mix has been exposed by brushing back the pointing to a recessed finish which allows the stone to be the dominant feature. The other photo below (right) shows historic pointing on an old outbuilding where roof tiles were used to fill in larger gaps between the stones, adding to its particular character and appearance.

If you need further information, or advice on sources of materials, or any clarification regarding the need for listed building consent or planning permission before re-pointing or rendering a traditional building, get in touch with our Building Conservation Team.