Welsh Slate Research Articles

Elwyn Tudor Jones

Elwyn Tudor Jones was a GP in rural north Wales for 30 years. During this time, while remaining what might be regarded as a traditional, “old-fashioned” practitioner, who knew his...

Quarrying for World Heritage Designation: Slate Tourism in North Wales

During the height of the Industrial Revolution, North Wales was the largest global producer of slate. Welsh slate was extensively utilized as a roofing material by industrializing countries around the world in the late nineteenth century. Although several surface quarries remain open, the last underground slate mines in Wales closed in the 1960s. An industry that once employed more than 17,000 now supports 400 jobs in the region. Today, slate tourism sites tell the story of this important aspect of North Wales’ industrial and geologic heritage. In 2012, a “Slate Industry of Wales” site was nominated to the UNESCO World Heritage Tentative List by the UK. Though Welsh coal tourism sites have been widely analyzed in the literature, few studies have investigated the country’s slate tourism. This paper explores the interpretive discourses presented at three prominent slate tourism attractions in North Wales and compares them with the justifications provided for World Heritage designation. Among the themes discussed are the importance of Welsh slate, geo-interpretation, slate technology, the life of Welsh quarrymen, and impacts of slate mining.

2016 年の地質鉱物関連英文ニュース誌の話題 「鉱物資源開発，石材，地域地質，および地球科学俯瞰」

Information collected from geological newsmagazines in 2016 is reviewed. First topic is mineral resources such as mineral commodity summary of 2015 in USA and future of phosphate resource. Second topic is building stones such as Welsh Slate and Portland Stone. Gravestone geology is also discussed. Third topic is regional geology. This topic focuses Geology of Cuba. Fourth topic is current status of geoscience in global changing and a remarks on the classification for diorite and syenite.

Chronic obstructive pulmonary disease in Welsh slate miners.

Exposure to respirable crystalline silica (RCS) causes emphysema, airflow limitation and chronic obstructive pulmonary disease (COPD). Slate miners are exposed to slate dust containing RCS but their COPD risk has not previously been studied. To study the cumulative effect of mining on lung function and risk of COPD in a cohort of Welsh slate miners and whether these were independent of smoking and pneumoconiosis. The study was based on a secondary analysis of Medical Research Council (MRC) survey data. COPD was defined as forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) ratio <0.7. We created multivariable models to assess the association between mining and lung function after adjusting for age and smoking status. We used linear regression models for FEV1 and FVC and logistic regression for COPD. In the original MRC study, 1255 men participated (726 slate miners, 529 unexposed non-miners). COPD was significantly more common in miners (n = 213, 33%) than non-miners (n = 120, 26%), P < 0.05. There was no statistically significant difference in risk of COPD between miners and non-miners when analysis was limited to non-smokers or those without radiographic evidence of pneumoconiosis. After adjustment for smoking, slate mining was associated with a reduction in %predicted FEV1 [β coefficient = -3.97, 95% confidence interval (CI) -6.65, -1.29] and FVC (β coefficient = -2.32, 95% CI -4.31, -0.33) and increased risk of COPD (odds ratio: 1.38, 95% CI 1.06, 1.81). Slate mining may reduce lung function and increase the incidence of COPD independently of smoking and pneumoconiosis.

Cambrian age Welsh Slate: A Global Heritage Stone Resource from the United Kingdom

Slate from the Cambrian succession of North Wales is a well-known source of building products from the United Kingdom and is here advocated as a suitable Global Heritage Stone Resource. Its first recorded use was in the Roman period in Wales, and subsequently from the sixteenth century throughout the British Isles. During the 16th and 17th centuries several small companies worked the slate belt from Bethesda to the Nantlle valley but in the mid-18th these were gradually taken over or amalgamated and three large operations came to dominate the industry: Penrhyn, Dinorwic, and the Moel Tryfan to Dorothea group of quarries. From the late eighteenth century production expanded rapidly supplying markets worldwide especially to northern Europe and the British colonies. Slate has been used in all its forms but most notably as roofing slates in the construction of buildings at all levels in society and for buildings of the highest historical and architectural importance. Modernisation of the industry has enabled Cambrian Welsh Slate to continue to be quarried today in an environmentally sensitive manner by Welsh Slate Ltd.

Front and Back Covers, Volume 31, Number 6. December 2015

Front and back cover caption, volume 31 issue 6Front coverAI and humanityA statue by Stephen Kettle of Alan Turing, sitting pensively at one of his code‐breaking machines in Bletchley Park. Made up from half a million pieces of Welsh slate, this statue was a landmark feature for the Life and Works of Alan Turing exhibition in 2012, which was curated following a public campaign to save the Turing‐Newman Collaboration Collection, a rare collection of his mathematical papers. Members of the Turing family additionally contributed some of the mathematician's personal belongings, including a teddy bear he used to practise his lectures on.Bletchley Park is now a huge heritage attraction, more so since The Imitation Game, a film based on the life of the pioneering computer scientist, came out.Previously known as the UK Government Code and Cypher School, this is now a site for the National Museum of Computing, which ncludes the huts and blocks that hosted a group of codebreakers whose work is said to have helped shorten the war by two years.In this issue, Ting Guo looks at Turing's personal trajectory in life and asks to what extent his search for artificial intelligence was inspired by considerations other than purely technical ones. To design artificial intelligence is to reproduce what is the essential ‘us’, what Pamela McCorduck refers to as an ‘odd form of self‐reproduction’. The desire for such machines, she argues, is a desire equally rooted in fear and allure, which reflects not only the drive for knowledge and human progress, but the discovery of the human self, which is itself driven by fundamental problems of being human.Back coverWORLDS IN MINIATUREMiniature worlds fascinate us. Taking familiar objects, scenes and environments and scaling them down to the minute generates a sense of wonder, forming a special connection between object and audience across which information can flow in subtle and unexpected ways.For centuries, people have used miniaturization to create tiny settlements with streets down which traffic doesn't flow and shops where no purchases are made. In doing so, they generate a fantasy, an idealized portrayal of a world they wish to see, not the one they inhabit.One of the most famous of these miniature communities is Madurodam in the Netherlands. Attracting more than 700,000 visitors a year, this park seeks to replicate particular dioramas of Dutch life, employing a dedicated team of professional modellers focusing on specific aspects of Dutch architecture and urban environments to portray a particular, explicitly positive, image of the Netherlands.The choices made at this site, and others like it all over the world, are part of a complex process of representation in miniature, a selection of iconography and design intentionally assembled to create unconscious impressions in visiting tourists, particularly children, about the full‐sized communities they resemble. As such, their representative powers are partial, a carefully curated miniature snapshot of certain aspects of an entire nation designed to act as a cultural and educational ambassador.In this issue, Jack Davy explores how the process of miniaturization, as evidenced by a Lego figurine, can encapsulate and transmit complex and controversial themes in a child‐like, non‐threatening manner. These processes operate subtly and inexplicitly, shaping our understanding of the wider world around us through the affordances of the small.

Consolidation and repair of a heather-thatched barn

The Black Barn (Figure 1) at Tow House in the South Tyne Valley west of Hexham in Northumberland is a small heather-thatched cruck-framed building dating from the early 18th century. A rare survivor of a widespread vernacular building type in the north of England, it is Listed as Grade II*, retaining significant original heather thatch in its base coat and ridge covering as well as all the primary timbers of its cruck roof construction.Before the mid-19th century heather thatching was a predominant roof covering in the English uplands where the material was abundant and easily transported, but by the beginning of the 20th century the skills in thatching had been largely lost in the face of the cheap distribution by rail of more durable Welsh slate. Thatchers themselves have played down the longevity of heather thatch and in any case the management of heather moorland for sheep grazing and sporting purposes yields unsuitable material for thatching.English Heritage, who have supported this project throughout, are keen to develop and promote an understanding of traditional building skills in England, and the opportunity to study this 300-year-old thatched barn has shown that it is possible to reveal past practices in order to inform a thorough repair programme and ensure sound future maintenance.

Towards International Designation of a Heritage Dimension Stone

The Global Heritage Stone Resource (GHSR) designation has been proposed to recognise dimension stone types that have achieved important utilisation in human culture. Within internationally recognised rules, a GHSR will be determined on the basis of significant use in human history, wide geographic range of utilisation, and the benefits that would accrue from designation. Nominations will include a detailed description that allows professionals to introduce new scientific terminology, define geotechnical properties, identify the specific geographic/geological occurrence, and also the characteristic texture, colour and variability that contribute to aesthetic suitability for use. GHSR designation will have significant value for all professional groups that work with stone. The necessary GHSR delineation, including current and former quarry sources, will help to facilitate the safeguarding of resources for future use. Specific GHSR geotechnical characteristics associated with a formal name could also aid the development of specific geographical designations for stone, similar to those being currently applied in the European Union for foodstuffs. The international rules will provide a succinct pathway for GHSR designation with the assistance of a governing Board. A draft check list of essential GHSR properties has been prepared and tested using trial citations for “Portland Stone” and “Welsh Slate” from the United Kingdom.

A Slate Saw Mill at Twll Coed Slate Quarry in the Nantlle Valley, Gwynedd

A 19th-century slate sawing machine from the saw mill at the disused Twll Coed Slate quarry, in the Nantlle valley, Gwynedd, is to be added to the National Collection of slate quarrying artefacts at the Welsh Slate Museum, Gilfach Ddu, Llanberis. The opportunity was taken before its removal to carry out a detailed study of the machine itself and to carry out a photographic record of the mill building. Whilst the slate industry of Wales has had the benefit of much archaeological study, this has tended to concentrate on whole-quarry surveys. The opportunity to carry out a detailed recording of a slate-saw table and the mill building in which it was housed prior to the removal of the machine sheds light not only on the process by which the industry was mechanised in its 19th-century heyday but also on the way in which it reverted to smaller-scale technology in the harsher climate of the 20th century. Slate saw mills were central to this process, marking the move away from working by barely capitalised independent quarryman-proprietors to highly capitalised factory type production, and in this case a reversion to smaller production units thereafter.

The streets of Bethesda: The slate quarrier and the Welsh language in the Welsh Liberal imagination

Sociolinguistic debates about the fate of the Welsh language have since at least the mid-20th century posited the relationship between language and political economy as a central factor in the death or rebirth of the Welsh language since the Industrial Revolution. Such studies have been concerned primarily with empirical head counts of actual speakers and the movements of populations and distributions of languages as determined by political economic independent variables. This article argues that the relationship between language and political economy was also crucially and consequentially construed in the 19th century in terms of “imagined” exemplary speakers of Welsh. In the imagined voice of the Welsh slate quarrier, Welsh elites of the 19th century found a “modern” Welsh-speaking figure who participated in industry while remaining Welsh, both linguistically and culturally, thereby associating the Welsh language itself with the desirable properties of modernity, particularly industrial productivity, and this allowed it to be imagined as a language at home in modernity.The research for this paper was made possible by a Reed College faculty grant and the friendship and generosity of Dylan Morgan and his family. Versions of this material have been presented at the AAA in San Francisco and Bard College, and I would like to thank my fellow participants and audiences there for their helpful comments. I would like to thank Richard Bauman, Mario Bick, Steve Coleman, Elizabeth Duquette, David Garrett, Alex Hrycak, and Rupert Stasch for comments and encouragement, as well as Jane Hill and the anonymous reviewers provided by Language in Society. Errors are my own.

English Money and Welsh Rocks: Divisions of Language and Divisions of Labor in Nineteenth-Century Welsh Slate Quarries

In 1893 a Welsh poet with the bardic name Glan Elsi uttered a remarkable vaticination that seemed to unite the fate of the Welsh language and the Welsh slate quarrier:Dearest old Welsh, if ever it dies,From the lips of a quarrier, I think, will come the final word.John Owen (Glan Elsi), “Y Chwarelwr” [The quarrier]. Cymru 5, 1893, p. 112.What is immediately remarkable is that such an identification of a modern proletariat (as opposed, for example, to a vanishing traditional peasantry, as would be so common elsewhere in Europe), as a linguistic kulturträger of the Welsh language was by this time so unremarkable. Even more extraordinary, perhaps, is that this was a by-product of the slate-quarriers' own self-mythologizing.

Networking for marketing advantage

States that networking theories have attracted increasing attention during the 1990s – although the network concept is certainly not new. Looks at the computer industry in Silicone Valley, California and the textile industry in Prato, central Italy. Discusses co‐operative behaviour and the relative advantages derived from such arrangements. Examines the slate industry in North Wales and, specifically, the decision by six long‐established slate quarries to come together to market their common product and promote Welsh slate at a global level. Aims to look at the industry’s past, present and future trends discovering how this inter‐firm collaboration aims to turn around the plight of industry.

Compaction fabrics of pelites: experimental consolidation of kaolinite and implications for analysis of strain in slate

Compaction of clay and shale results in large reductions in volume as pore water is expelled. Preferred orientation of the platy minerals increases with compaction strain and loss of porosity according to the March-Owens model. This relationship has been studied quantitatively by experimentally consolidating kaolinite clay from slurries and analyzing the resulting fabrics with the X-ray pole figure goniometer and scanning electron microscope (SEM). ‘Initial’ porosity corresponds to the onset of the strain recorded by the preferred orientation; and the values of 0.78 for dispersed slurries and 0.76 for flocculated slurries reflect the electrostatic forces between the clay platelets. ‘Initial’ porosities of recently deposited fine silt and clay are in the range of 0.60-0.90 and are a function of grain size and mineralogy. Loss of this ‘initial’ porosity has a large effect on the subsequent development of slaty cleavage. Matrix methods were used to model deformation paths for slates in the Welsh slate belt. Preferred orientation of mica and ellipsoidal shapes of ‘reduction’ spots were simulated for one locality by loss of a 0.60 ‘initial’ porosity, a 6° tilt of the beds and horizontal shortening involving plane strain. Strain determinations for shales and slates should include the large reduction in volume.

Comparison of strain and magnetic fabrics in Dalradian rocks from the southwest Highlands of Scotland

The magnetic fabrics of 235 samples from 31 localities in Argyllshire, Scotland were determined to study the development of the Caledonian tectonic fabric in the southwest Highlands of Scotland. The regional fabric indicates a strong NE-SW compressional foliation due to the primary deformational phases, which in parts has been overprinted by secondary deformations. A detailed comparison of the anisotropy data and the available strain data shows that the two fabric ellipsoids are co-axial, and that their axial mean ratios seem to be related by an empirical power relationship of the type: Xi Xj = li lj a (for i = 1,2,3; j = 1,2,3 and i ≠ j) where χ i and χ j are orthogonal principal axes and l i and l j are the corresponding orthogonal principal strain axes. The exponent a for the sites from Scotland is 0.088 ± 0.017 compared with 0.142 ± 0.001 and 0.145 ± 0.005 found in the Caledonian slates of the English Lake District and the Welsh slate belt.

Roofing Belfast and Dublin, 1896–98: American Penetration of the Irish Market for Welsh Slate

Roofing Belfast and Dublin, 1896–98: American Penetration of the Irish Market for Welsh Slate

The relationship between the magnetic and strain fabrics of some haematite-bearing Welsh slates

The anisotropy of magnetic susceptibility and the natural remanent magnetization of haematite-bearing Welsh Cambrian slates, showing a gradation in degree of deformation, have been related to the known strain of these rocks. An approximate quantitative relationship between strain and magnetic susceptibility anisotropy has been deduced, which would allow rapid strain estimation in this region by magnetic analysis.

Magnetic anisotropy and paleomagnetism

The natural remanent magnetization of certain Welsh slates lies in the cleavage plane, which was found to be a plane of high susceptibility defined by the alignment of anisotropic crystals of pyrrhotite. A correlation between the magnitude of susceptibility anisotropy and the bulk susceptibility of the slates has been observed. This is interpreted as a partial masking of the susceptibility anisotropy of the dispersion of magnetic particles by an isotropic contribution to the susceptibility of the rock due to the paramagnetic matrix. As a consequence of this masking, or dilution, rocks with low concentrations of hematite or pyrrhotite may be expected to exhibit susceptibility anisotropy which is small compared with that of the magnetic particles. Small susceptibility anisotropy controlled by the bedding plane has been observed in collections of sedimentary rocks including red sandstones. Laboratory experiments demonstrated that thermoremanent magnetization, isothermal remanent magnetization, and pressure-promoted remanent magnetization may be acquired anisotropically by rocks. Only certain red sandstones, of the rocks commonly used in paleomagnetism, appear to show a comparable divergence of the natural remanence from the geomagnetic field in which remanence was acquired.

Some Preliminary Measurements of Anisotropy of Magnetic Susceptibility of Rocks

summary Measurements have been made on four sets of rocks, two of which showed anisotropy of magnetic susceptibility and two were isotropic. The maximum and intermediate principal susceptibilities lie in the cleavage plane for some Welsh slates and in the horizontal plane for some igneous rocks of the Skaergaard layered intrusion. In both cases the directions of natural remanent magnetization have been affected. The two sets of isotropic rocks are from the northern Pyrenees and Deccan of India respectively. Both may have been affected by stress environments, the nature of which did not cause measurable anisotropy. It is unlikely that the directions of natural remanent magnetization have been affected for these rocks.

Anisotropy of Susceptibility and the Natural Remanent Magnetization of Some Welsh Slates

IN order to investigate the effect of the deformation associated with mountain building upon the aniso-tropy of susceptibility and the natural remanent magnetization of rocks, approximately a hundred specimens were prepared for measurement from some fifty samples of Lower Palaeozoic Welsh slates cleaved during the Caledonian orogeny. The anisotropy in fields of less than two œrsted was determined with a transformer bridge1 and the natural remanent magnetization with an astatic magnetometer. The results showed that the cleavage is a plane of high susceptibility, and that the remanent vector is parallel to it. In some of the slates it appears that the direction of natural remanent magnetization has been controlled by the anisotropic susceptibility, and in others that the pattern of anisotropy and the natural remanent magnetization have been aligned with the cleavage independently. I am indebted to Dr. J. C. Belshe and Dr. R. W. Girdler, with whose help the susceptibility work was begun.

Radiological surveys of working quarrymen and quarrying communities in Caernarvonshire.

Interest in the possible occupational lung diseases associated with slate-quarrying appears to date from the Registrar-General's Decennial Supplement, 1921, on Occupational Mortality (Registrar-General, 1927). Britten's review (Britten, 1928) showed that slate-masons and slate-workers had a significantly raised mortality from respiratory tuberculosis although it was much lower than that of tinand copper-miners. At roughly the same time, Wade (1927) called attention to the excessive mortality from tuberculosis of the slate-workers in the Gwyrfai rural district in North Wales. Since then, most of the references in the international literature about this subject have referred to Wales, but descriptions of cases of pneumoconiosis in slate quarry workers have been published in other countries. In France, Feil (1935) found relatively little pulmonary disease amongst slate-workers in May enne and Anjou. He attributed this to the low content of free silica (7%) in the slates there. In Germany, Schairer (1940) described egg-shell calcification in two slate workers; Koelsch (1950) described the radiographie appearances, and Ceelen (1951) described one case. In Italy, Frola (1942) described the radiographie appearances in 34 slate workers; and cases have been reported from the United States by Rogers (1932) and Mansur (1951). In Wales, Wade's report was followed by the survey by Sutherland and Bryson (1930) who found clinical evidence of pulmonary fibrosis amongst 56 out of 120 slate-quarrymen. A few years later Chalke (1933) showed that 28% of the tuberculous males in the county of Caernarvon were slate workers while this industry only absorbed 11 % of the male population. Davies (1939) reported the results of examining 117 slate-workers chiefly from Merionethshire and, as a result, silicosis amongst slate-workers who worked underground was scheduled under the Workmen's Compensation Act. The section of the industry involving work above ground was not so scheduled. Davies (1942) reviewed silicosis amongst coal-miners and slate workers in Wales. Later a committee of the Ministry of Works, under the chairmanship of Mr. F. Rees, reported on the Welsh slate industry (Ministry of Works, 1947). They considered that the fear of pneumoconiosis was preventing men entering the industry and recommended that the pneumoconiosis problem should be attacked at once. The relative position of tuberculosis mortality in the Gwyrfai rural district has not improved since the time of Wade's original investigation. In 1928 the tuberculosis death rate was 285 per 100,000 persons compared with a figure of 96 for England and Wales. In 1951 the figures were 110 and 31 respectively. In 1952 there was therefore evidence that pneumo coniosis?probably silicosis?was prevalent amongst slate-workers in North Wales, and that the tuber culosis death rate in the slate-quarrying areas was abnormally high. For these reasons, the Gwyrfai Rural District Council asked the Welsh Board of Health for an investigation, and as a result a survey was carried out by the Mass Radiography Service of the Welsh Regional Hospital Board in 1952-53, which is the subject of this paper.