: Casgliadau ac Ymchwil

Rydym yn parhau i nodi blwyddyn ryngwladol tabl cyfnodol yr elfennau cemegol ac, ar gyfer mis Ebrill, rydym wedi dewis calsiwm. Mae’r rhan fwyaf o bobl yn gwybod am galsiwm fel yr elfen sylfaenol er mwyn ffurfio esgyrn neu mewn calchfaen ond mae iddo lu o ddibenion eraill ac mae i'w gael ar wely'r môr ac mewn bywyd morol ddoe a heddiw.

Elfen fetelig o liw golau yw calsiwm (Ca) ac 20 yw ei rhif atomig. Mae’n hanfodol ar gyfer bywyd heddiw ac mae’n aml yn chwarae rhan bwysig yn cynnal planhigion ac anifeiliaid. Dim ond pedair elfen arall sy'n fwy cyffredin na chalsiwm yng nghramen y ddaear ac mae’n rhan o lawer o greigiau a mwynau fel calchfaen, aragonit, gypswm, dolomit, marmor a sialc.

Aragonit a calsit yw’r ddwy ffurf grisialog fwyaf cyffredin ar galsiwm carbonad ac fe gyfrannodd y ddwy at ffurfio’r ddwy filiwn o gregyn yn ein casgliad o folysgiaid. Craidd y casgliad hwn yw casgliad Melvill-Tomlin a gyfrannwyd i’r amgueddfa yn y 1950au. Dyma gasgliad rhyngwladol sy’n cynnwys llawer o sbesimenau prin, prydferth sy’n bwysig o safbwynt gwyddonol ac a ddefnyddir gan wyddonwyr o bedwar ban byd ar gyfer eu hymchwil. Caiff perlau, sydd hefyd wedi’u gwneud o aragonit a calsit, eu cynhyrchu gan gregyn deufalf fel wystrys, cregyn gleision dŵr croyw a hyd yn oed gregyn bylchog mawr. Ym myd natur, caiff perlau eu ffurfio wrth i’r molysgiaid ymateb i barasit ymwthiol neu ronyn o raean. Mae’r fantell o gwmpas corff meddal yr anifail yn gollwng calsiwm carbonad a conchiolin sy’n amgylchynu’r peth estron ac yn dynwared ei siâp ac felly nid yw pob un yn hollol grwn. Yn y diwydiant perlau, caiff pelenni bach iawn o gragen eu 'plannu’ yn yr wystrysen neu’r gragen las er mwyn sicrhau bod y berl a ffurfir yn hollol grwn.

Cyrff meddal sydd gan folysgiaid ac maent yn creu cregyn i fod yn darianau amddiffynnol iddynt. Mae hyn yn wir am anifeiliaid di-asgwrn-cefn eraill hefyd, yn enwedig yn y môr. Mae riffiau cwrel a thiwbiau rhai mwydod gwrychog (Serpulidae, Spirorbinae) yn dibynnu ar natur atgyfnerthol calsiwm carbonad i gynnal a gwarchod eu cyrff meddal. Mae gan gramenogion fel crancod a chimychiaid sgerbwd allanol caled sy’n cael ei atgyfnerthu â chalsiwm carbonad a chalsiwm ffosffad. O gastrolithau y daw’r calsiwm y mae ar gimychiaid, cimychiaid coch, cimychiaid afon a rhai crancod tir ei angen ar ôl bwrw’u cragen. (Weithiau, gelwir gastrolithau’n gerrig stumog neu'n llygaid crancod). Maent i’w cael ar y naill ochr a’r llall i’r stumog ac maent yn darparu calsiwm ar gyfer rhannau hanfodol o’r cwtigl fel darnau’r geg a’r coesau. Yng nghasgliad yr Amgueddfa, mae bron 750,000 o anifeiliad morol di-asgwrn-cefn, yn cynnwys cramenogion, cwrelau a mwydod gwrychog.

O fwynau calsiwm y gwnaed llawer o’r 700,000 o ffosilau sydd yng nghasgliadau’r Amgueddfa hefyd. Defnyddir dau brif fath o galsiwm carbonad i wneud cregyn a sgerbydau allanol anifeiliaid di-asgwrn-cefn, ac maent yn fwy tebygol o gael eu hanfarwoli fel ffosilau os defnyddir un ohonynt yn hytrach na’r llall. Mae aragonit, sydd yng nghregyn molysgiaid fel amonitau, gastropodau a chregyn deuglawr, yn ansefydlog ac nid yw’n para am filiynau o flynyddoedd gan amlaf. Wrth ffosileiddio, mae cregyn aragonit naill ai’n ymdoddi’n llwyr, neu mae’r aragonit yn ailgrisialu i ffurfio calsit. Defnyddiwyd calsit i wneud cregyn a sgerbydau grwpiau o gwrelau sydd wedi peidio â bod erbyn hyn, braciopodau cymalog, bryosoaid, ecinodermiaid a’r rhan fwyaf o drilobitau. Mae’n llawer mwy sefydlog nag aragonit ac felly mae darnau caled gwreiddiol o’r creaduriaid yn ymddangos fel ffosilau, filiynau o flynyddoedd ar ôl iddynt suddo i wely’r môr. Yn aml, gwelir grisialau mawr o galsit yn llenwi mannau gwag mewn ffosilau, fel y siambrau y tu mewn i gregyn amonitau. Mae fertebratau’n defnyddio mwyn calsiwm gwahanol i wneud esgyrn a dannedd: apatit (calsiwm ffosffad), a all bara am filiynau o flynyddoedd i wneud ffosilau eiconig fel sgerbydau deinosoriaid ac ysgithrau mamothiaid.

Yng nghasgliadau’r Amgueddfa o greigiau, mae llawer o galchfeini, creigiau a ffurfiwyd ar waelod y môr amser maith yn ôl o ddarnau o gregyn a deunydd arall sy’n cynnwys llawer o galsiwm carbonad. Ers miloedd o flynyddoedd, bu pobl yn defnyddio calchfeini i adeiladu: cerrig cerfiedig yn nhemlau eiconig y Groegiaid a’r Rhufeiniaid; darnau mâl i fod yn falast o dan reilffyrdd a ffyrdd; neu wedi’u llosgi i greu calch i wneud sment. Defnyddiwyd calchfaen enwog o Dorset o’r enw Carreg Portland i adeiladu Amgueddfa Genedlaethol Caerdydd ac adeiladau eiconig eraill yng Nghanolfan Ddinesig Caerdydd. Ar lawr yr Amgueddfa gwelir teils marmor, sef calchfaen a drawsnewidiwyd o dan wres a gwasgedd mawr. Bu cerflunwyr yn hoff iawn o farmor ers dyddiau’r hen Roegiaid a’r Rhufeiniaid. Yng nghasgliadau celf yr Amgueddfa gwelir gweithiau marmor gan Auguste Rodin, John Gibson, Syr Francis Chantrey, Syr William Goscombe John a llawer o rai eraill. Yn ogystal, mae yno enghreifftiau pwysig o waith gan gerflunwyr o’r ugeinfed ganrif, fel Jacob Epstein, Eric Gill a Henri Gaudier-Breszka. Roedd yn well ganddyn nhw gerfio calchfaen feddalach a llai dwys, Carreg Portland a thywodfaen.

Locust swarms have for centuries destroyed crops and threatened food supplies across large parts of Africa, the Middle East, and Asia. This threat continues today - a recent plague in Madagascar destroyed 2.3 million hectares of crops. Controlling it took three years and cost $37 million.

Desert Locust (Schistocerca gregaria) swarms can move hundreds of miles within a vast ‘invasion area’ that can span dozens of countries, and even continents. To better understand and control such plagues of locusts the British founded the Anti-Locust Research Centre (ALRC) in the 1920s.

The ALRC took the lead in monitoring, studying, forecasting and controlling locust swarms. To do this they had to work with different experts including entomologists (insect specialists), cartographers (map makers), toxicologists (experts on poison), explorers, photographers, the military and local people.

For decades the ALRC gathered information on locusts worldwide. This now forms an incredible archive of thousands of documents, maps and photographs held at the Natural History Museum in London, and a collection of over 70,000 locust specimens that are now part of the collections here at Amgueddfa Cymru.

Our new display ‘Locust War’ reunites the archive and specimens to rediscover the remarkable work of the ALRC and the challenges it faced to understand and control the desert locust.

The exhibition is the work of a collaborative research project led by academics from the University of Warwick, University of Portsmouth and Glasgow School of Art, and supported by the Arts and Humanities Research Council.

‘Locust War’ is part of the displays in our InSight Gallery, and runs until the 16^th September 2019.

Many of the books in the Library collections at the National Museum Wales have attractive decorative techniques applied to the covers or text blocks. Decoration on text blocks, the combined pages of the book inside the covers, is particularly lovely because it tends to be hidden when they are on the shelves.

The most popular examples of decorating text blocks include marbling and gilding. But one of the most interesting techniques is the one known as disappearing fore-edge painting, which was often hidden underneath the other types of decoration.

Fore-edge painting was a technique that reached the height of its popularity from the mid-17th century onwards. It was usually applied to the longest section of the text block, the one opposite the spine, the fore-edge.

Two books in our special collections feature examples of mid-19th century disappearing fore-edge paintings. They are the two volumes of the second edition of the Memoirs of Lord Bolingbroke by George Wingrove Cooke, and were published in 1836.

When the book is closed you cannot see the image, only the gilt edges of the text block, but when the leaves are fanned, the hidden picture is revealed.

To achieve this effect, the artist would need to fan the pages, and then secure them in a vice, this means they are applying the paint not to the edge of the page, but to just shy of the edge. Once completed, it is released from the vice and the gilding would be applied to the edges.

Landscape scenes were the most popular for this technique, and the ones on our books show Conway Castle and Caernarfon Castle.

Very often the motivation for a fore-edge painting was a demonstration of artistic skill, so it didn’t always follow that the images were related to the text contained within the book. These two volumes of Memoirs, do not have an obvious connection to the scenes painted. Lord Bolingbroke (Henry St John, 1st Viscount Bolingbroke 1678–1751) was an English politician during the reign of Queen Anne, and later George I, and is probably best known as a supporter of the Jacobite rebellion of 1715, but he does not appear to have any direct association with either Conwy or Caernarfon.

The volumes were acquired for the Library in 2008 from a rare book dealer, but we don’t know enough about their history to be able to tell when the fore-edge paintings were added. The first volume contains an inscription that states that the book was a gift to a T. M. Townley from his friend Samuel Thomas Abbot on his leaving Eton in 1843. Unfortunately we don’t know anything about either the recipient or the sender, so we can’t tell if one of them was ultimately responsible for painting the books.

Each week, hundreds of people will walk through the front doors of the National Museum Cardiff. Yet despite visiting the exhibitions on display, many will be oblivious to what goes on in the background. Conducting a work experience placement at the museum gave us a rare insight into how much work and effort goes on behind closed doors.

With the intention of creating a video for the Saving Treasures, Telling Stories project, we were taken on a tour around the archaeology department on our first day of placement. We were fortunate to be shown around the stores, where many remarkable items were kept for preservation and research. Some of the items we viewed were Roman and prehistoric pots, vases and burial urns, which allowed us to explore how communities and cultures operated thousands of years ago.

The following day we attended Cyfarthfa Museum in Merthyr Tydfil, which is to acquire a hoard of five Roman Denarii, with thanks to funding from the Saving Treasures project. We filmed museum staff and the finders of the hoard, and heard about its significance. It was great to see the enthusiasm of the metal detectorists who discovered the hoard, and how proud they were of their achievement.

We spent the next few days editing the video together back at the University of South Wales campus. This proved to be a difficult job, as there were so many great shots to choose from, so it was difficult to decide which to cut out. However, the staff were always on hand to answer any questions we had and help out where possible.

Working at the National Museum Cardiff was a wonderful experience, and we were able to appreciate just how much work goes on behind closed doors to create the exhibitions we see. This work and research has helped us to understand history and past cultures in greater detail, and we would like to thank all the staff for their friendliness and a great week.

Were you amongst among the record number of people who enjoyed our recent ‘Tim Peake’ and ‘Leonardo da Vinci’ exhibitions at National Museum Cardiff? Did you realise that, while you were in the public galleries, there were workers with hard hats and power tools working to improve the building?

We are currently undertaking a large amount of maintenance works in the museum. We do this in such a way to minimise the disturbance to our visitors as much as possible. We want you to enjoy your experience at the museum and be inspired. During the coming months, however, scaffolding will be erected around parts of the building. We are also going to get a temporary over roof on the oldest part of the museum.

Given that this part of the building was opened as long ago as April 1927 by King George V it is now due some tender loving care. Owing to the ravages of time, the roof has developed a few leaks which we are going to repair this year. This also involves having to close some galleries temporarily, for example the Ceramics and Photography galleries. We do apologise for the inconvenience, but these closures are necessary to allow us to undertake the work on the roof and associated internal works.

Galleries will reopen refreshed in the Autumn of 2019, once the works are completed. The brilliant news is that we will be able to present exhibitions without having to worry about a leaking roof. Associated electrical rewiring will also reduce the fire risk in the museum.

Other works we are undertaking - unbeknown to most people as these are happening in our basement - are further electrical works and substantial improvements to our air conditioning systems. This includes the installation of new air conditioning equipment to replace old equipment which will make the museum much more environmentally sustainable.

We are undertaking these works, with kind support of Welsh Government, to protect the Welsh national collection. We constantly strive to improve the way we care for the three million objects housed at National Museum Cardiff. The collections allow us to refresh displays regularly and put on exhibitions with new themes – check out our new ‘People and Plants’ exhibition of the museum’s economic Botany collection. Collections are also used for research, study, teaching, commemoration and many other functions.

Hence, there are many reasons why we would want to do our best to preserve the collections as best we can. The maintenance works during the coming months will greatly assist us with our collection care and, if these occasionally impact on our public spaces, we do ask that you bear with us – the works are temporary but the benefits will be long-lasting.

Find out more about Care of Collections at Amgueddfa Cymru - National Museum Wales here and follow us on Twitter. Follow the progress of the maintenance works during the coming months in 2019 on Twitter using the hashtag #museumcare.