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Wrth ymweld ag Eryri ar ei daith drwy Gymru yn 1188, gwelodd Gerallt Gymro ddarn o dir yn nofio ar wyneb y llyn a adwaenwn heddiw fel Llyn y Dywarchen, ger Rhyd-ddu yn Eryri. Fe’i disgrifiodd yn hanes ei daith fel insula erratica, sef ‘ynys wibiol’ yn ôl cyfieithiad Thomas Jones, ac un ‘sydd yn crwydro ar brydiau, gan rym y gwyntoedd yn ei gyrru, i rannau cyferbyn y llyn. Yma bydd y bugeiliaid yn rhyfeddu’n aml ddarfod trosglwyddo’n sydyn eu gyrroedd wrth bori, i fannau pell i ffwrdd.’
[Gerallt Gymro: Hanes y Daith trwy Gymru, gol. Thomas Jones (Caerdydd, 1939), 139. Armentum yw gair Gerallt Gymro am ‘gyrroedd’ yma yn ei Iterarium Kambriae, II.ix, sef ‘herd of cattle’ yn ôl y Dictionary of Medieval Latin from British Sources.]
Yn ei daith yntau drwy Gymru tua 1536–9, cyfeiriodd John Leland at y llyn fel Lin edwarchen (‘Llyn y Dywarchen’) a disgrifio’r ynys fel “Swymming Island, and ther of it hath the name as of a suimming swarth of yerth.” Dyma’r cyfeiriad cynharaf at yr enw, yn ôl Archif Melville Richards.
[L.T. Toulmin Smith (ed.), The Itinerary of John Leland in or about the Years 1535–1543 (London, 1906–10), 74.]
Braidd yn ddrwgdybus oedd John Speed o fodolaeth y fath ynys wrth iddo gyfeirio at ddisgrifiad Gerallt Gymro ar ddechrau’r ail ganrif ar bymtheg; ond eto mae’n cyfaddef bod angen ymweld â’r llyn cyn gwrthod yr hanes yn llwyr:
“there is a moveable Iland, which as soone as a man treadeth on, it forthwith floateth a great way off, whereby the Welsh are said to have often scaped and deluded their enemies assailing them: these matters are out of my Creed, and yet I think the reader had rather believe them, then go and see whether it be so or no.”
[John Speed, Theatre of the Empire of Great Britain (London, 1627), ii. 123.]
Ym mis Mai 1697, daeth y gwyddonydd nodedig Edmund Halley i Eryri – y dyn a gysylltwn yn bennaf heddiw â’r gomed sydd wedi ei henwi ar ei ôl, ac sydd i’w gweld bob rhyw 75 neu 76 o flynyddoedd. Roedd am ddangos bod modd cyfrifio uchder mynydd drwy fesur hyd colofn o fercwri mewn baromedr ar wahanol lefelau – ei ‘Torricellian Experiment’. Cymerodd fesuriadau ar ben yr Wyddfa, wrth droed yr Wyddfa yn Llanberis yn ddiweddarach ar yr un diwrnod, ac yna ar lefel y môr yng Nghaernarfon ar y diwrnod canlynol.
Yn ystod ei ymweliad mae’n amlwg i Halley glywed am hanes rhyfeddol yr ynys symudol, a phenderfynodd ymweld â’r llyn er mwyn casglu tystiolaeth drosto ei hun, yn enwedig gan fod cyfrol newydd ei chyhoeddi, meddai, yn gwadu bodolaeth y fath ynys.
Pan gyrhaeddodd y llyn, roedd y dywarchen ar y ‘lee shore’, meddai, felly camodd arni, a pheri iddi nofio o’r lan (‘I launched it off and swam it’), er mwyn cadarnhau ei bod yn rhydd. Ystyr swim yma yw ‘to cause (something) to pass over the surface of water’ (OED Ar lein) – felly ni chredaf fod Halley yn dweud iddo nofio yn y dŵr ei hun i archwilio’r dywarchen, fel y mae rhai awduron yn honni. Cadarnhaodd mai darn o dir mawn wedi ymryddhau o’r dorlan ydoedd, ac ar ôl holi pobl leol, dysgodd fod y dywarchen yn llai nag y bu, a’i bod wedi hollti’n ddwy ran am gyfnod, ond bod y rhan lai (y ‘lesser spot’, fel y’i disgrifir isod) bellach wedi diflannu. Cyhoeddodd Halley ei adroddiad yn rhifyn 1697 y Philosophical Transactions:
An Account of Snowdown-Hill by Mr. Edmund Halley
“I think we saw as far as St. David’s Head into the South, Carnarvonshire and Anglesey lay under us, like a Map, affording a very pleasant Prospect, were it not for the Horrours of the Neighbouring Precipices. Hence we counted fifteen or sixteen Lakes, great and small, where the Cavities of the Rocks are filled up with the Rills that gleet from the Hills; all these are said to abound with Trouts, some of which we found to be especial good Fish: And in one of these Lakes I was on board a floating Island, as it may be called; the Lake is scarce half a Mile about, environed with a boggy turfy Soil, a Piece of which, about 6 Yards long and 4 broad, floats on the Water, being about five or six Inches raised above it; but it [is], I believe, about eighteen Inches deep within the Water, having broad spreading fungous Roots on its Sides, the lightness of which Buoys it up. It was driven on the Lee Shore, but I launched it off and swam it, to be satisfied it floated: This I take the more notice of, because it is denied to be true, by the Author of the Additions to Cambden [sic], lately Published: But I myself saw it as described, and was told it had formerly been bigger; there being a lesser spot, that they told us, had been heretofore a part thereof, which floated likewise.”
[Philosophical Transactions (London, 1697), 537–8.]
Fel y gwelir mae Halley yn awgrymu nad oedd awdur yr ychwanegiadau i waith Camden yn credu bod yn ynys yn bodoli. Nid yw hynny’n hollol wir. Gallwn fod yn hyderus mai at argraffiad 1695 o waith Camden y mae Halley yn cyfeirio; daeth hwnnw allan dwy flynedd cyn iddo ymweld ag Eryri. Ynddo cafwyd cyfieithad newydd o Britannia Camden dan olygyddiaeth Edmund Gibson, a oedd wedi gofyn i Edward Lhwyd ychwanegu at y rhannau Cymreig. Lhwyd felly yw’r ‘Author of the Addition to Cambden [sic]’, a chyhoeddwyd ei ychwanegiadau ar ddiwedd cofnod pob sir. Nid yw Lhwyd yn gwadu bodolaeth yr ynys fel y cyfryw, ond mae’n gwneud yn fach ohoni a’i galw’n ‘little green patch’, gan synnu fod pobl yn rhoi cymaint o sylw iddi. Ar ôl cyfeirio at ddisgrifiad Gerallt Gymro, meddai:
“The Lake wherein he tells us there’s a wandring Island, is a small pond, call’d Lhyn y Dywarchen, (i.e. Lacus cespitus,) from a little green patch near the brink of it, which is all the occasion of the fable of the wandring Island.”
[W. Camden, Britannia, newly translated … by Edmund Gibson, with annotations to the text (London, 1695), 669].
Tybed ai’r hyn a welodd Lhwyd (neu ei ffynhonnell) oedd y ‘lesser spot’ a welodd Halley, sef y darn bychan o’r dywarchen a oedd wedi dod yn rhydd o’r brif ran; ac a fethodd weld y brif dywarchen gan ei bod yn ymyl y lan, ac felly’n edrych fel rhan o’r tir? Beth bynnag, mae’n amlwg fod Halley yn teimlo nad oedd Lhwyd wedi gwneud cyfiawnder â maint y brif dywarchen.
Bu Thomas Pennant yntau’n crwydro yn yr ardal yn y 1770au cynnar, ac mae’n debygol mai dyma pryd y gwelodd yntau’r llyn a’r dywarchen yn nofio arni. Disgrifiodd yr olygfa fel a ganlyn yn 1781:
“Llyn y Dywarchen, or The Lake of the Sod … It had on it a floating island, of an irregular shape, and about nine yards long. It appeared to be only a piece of the turbery, undermined by the water, torn off, and kept together by the close entangling of the roots, which form that species of ground. It frequently is set in motion by the wind; often joins its native banks; and, as Giraldus says, cattle are frequently surprized on it, and by another gale carried a short voyage from the shore.”
[Thomas Pennant, A Journey to Snowdon (London, 1781), 180, a hefyd Tours in Wales (1784), ii. 187–8. (Diolch i Mary-Ann Constantine am y cyfeiriadau hyn.)]
Nid yw’r dywarchen neu’r ynys symudol yn bodoli bellach, ond mae’n amlwg iddi fod yn un sylweddol, gan iddi oroesi o ddyddiau Gerallt Gymro hyd at y cyfnod modern – er ei bod yn ansicr pryd yn union y diflannodd. Fodd bynnag, mae’n amlwg nad yr un yw’r dywarchen â’r ynys ansymudol a welir yng nghanol y llyn heddiw fel yr honnodd J. Lloyd-Jones, er enghraifft, yn ei astudiaeth safonol o enwau lleoedd sir Gaernarfon. [J. Lloyd-Jones, Enwau Lleoedd Sir Gaernarfon (Caerdydd, 1928), 91, ‘Llyn y Dywarchen, ger Rhyd-ddu, oddi wrth yr ynys fechan yn ei ganol’.] Fel yr esboniodd T.H. Parry-Williams:
“Y mae clampen o ynys rugog, greigiog, yn sownd a solet yn ei ganol er pan wyf i’n cofio; ond nid yr ynys hon ydyw’r ‘Dywarchen’ y cyfeirir ati yn ei enw ychwaith. ‘Tywarchen’ ydoedd honno ͏– talp neu ysglisen go helaeth o dir ͏– wedi ymryddhau o’r glannau ac a fyddai’n nofio ar hyd wyneb y llyn at drugaredd y gwynt. Gallai defaid gerdded iddi a phori arni pan ddelai at y lan, ac ar gefn hynny gael gwibdaith yma a thraw hyd y llyn … Gyda llaw, ni welais i erioed y wir dywarchen, i fod yn hollol siŵr. Efallai mai ymddangos yn gyfnodol yn y llyn y bydd hi, fel y bydd planed yn yr wybren.”
[T.H. Parry-Williams, O’r Pedwar Gwynt (Dinbych, 1944), 70. Diolch i Philip Henry Jones am y cyfeiriad.]
Mae’n debygol fod y dywarchen wedi diflannu erbyn y 1890au, cyfnod plentyndod T.H. Parry-Williams. Tybed ai ei holion a welir ar fap yr Arolwg Ordnans, yn agos i’r gwaelod ar y dde?
Llyn y Dywarchen
When visiting Eryri on his journey through Wales in 1188, Gerald of Wales saw a piece of turf floating on the surface of the lake we know today as Llyn y Dywarchen, near Rhyd-ddu. In his account of the journey he described it as an insula erratica which Lewis Thorpe translates as ‘a floating island’, and one ‘which moves about and is often driven to the opposite side by the force of the winds. Shepherds are amazed to see the flocks which are feeding there carried off to distant parts of the lake.’
[Gerald of Wales, The Journey through Wales, ed. Lewis Thorpe (Harmondsworth, 1978), 194. Gerald’s word for Lewis’s ‘flocks’ here is armentum in his Iterarium Kambriae, II.ix, namely a ‘herd of cattle’ according to the Dictionary of Medieval Latin from British Sources, so Gerald probably saw cattle on the island and not sheep.]
John Leland, in his journey through Wales in around 1536–9, referred to the lake as Lin edwarchen – Llyn y Dywarchen ‘Lake of the Sod’ – and described the island as a ‘Swymming Island, and ther of it hath the name as of a suimming swarth of yerth’. This is the earliest reference to the name, according to Melville Richards’s Welsh Place-name Archive.
[L.T. Toulmin Smith (ed.), The Itinerary of John Leland in or about the Years 1535–1543 (London, 1906–10), 74.]
John Speed was rather uncertain of the existence of such an island when he referred to Gerald of Wales’s description at the beginning of the seventeenth century; but admits that it would be better to visit the lake before rejecting the account completely:
“there is a moveable Iland, which as soone as a man treadeth on, it forthwith floateth a great way off, whereby the Welsh are said to have often scaped and deluded their enemies assailing them: these matters are out of my Creed, and yet I think the reader had rather believe them, then go and see whether it be so or no.”
[John Speed, Theatre of the Empire of Great Britain (London, 1627), ii. 123.]
In May 1697, the eminent scientist Edmund Halley came to Eryri. We associate Halley today mainly with the comet named after him, which appears every 75 or 76 years. He wanted to demonstrate that it was possible to calculate the height of a mountain by measuring a column of mercury in a barometer at different levels – he called this his ‘Torricellian Experiment’. He took measurements on top of Yr Wyddfa, at the foot of Yr Wyddfa at Llanberis later on the same day, and then at sea level in Caernarfon on the following day.
During his visit Halley heard about the amazing floating island and decided to visit the lake to investigate it, especially as a newly-published volume had denied the existence of such an island.
When Halley reached the lake, he found the island on the ‘lee shore’ and stepped onto it, and caused it to swim from the shore, to confirm that it floated. Swim here means ‘to cause (something) to pass over the surface of water’ (OED Online) – so I don’t think that Halley is claiming that he swam in the water to explore the turf, as some authors have claimed. He confirmed that it was a piece of peaty turf that had detached itself from the bank and, after questioning locals, he learned that the turf was much smaller than it had been in the past, and that it had split in two for a while but that the smaller part, the ‘lesser spot’ as he describes it below, had by now disappeared. Halley published an account of his visit in the 1697 issue of the Philosophical Transactions:
An Account of Snowdown-Hill by Mr. Edmund Halley
“I think we saw as far as St. David’s Head into the South, Carnarvonshire and Anglesey lay under us, like a Map, affording a very pleasant Prospect, were it not for the Horrours of the Neighbouring Precipices. Hence we counted fifteen or sixteen Lakes, great and small, where the Cavities of the Rocks are filled up with the Rills that gleet from the Hills; all these are said to abound with Trouts, some of which we found to be especial good Fish: And in one of these Lakes I was on board a floating Island, as it may be called; the Lake is scarce half a Mile about, environed with a boggy turfy Soil, a Piece of which, about 6 Yards long and 4 broad, floats on the Water, being about five or six Inches raised above it; but it [is], I believe, about eighteen Inches deep within the Water, having broad spreading fungous Roots on its Sides, the lightness of which Buoys it up. It was driven on the Lee Shore, but I launched it off and swam it, to be satisfied it floated: This I take the more notice of, because it is denied to be true, by the Author of the Additions to Cambden [sic], lately Published: But I myself saw it as described, and was told it had formerly been bigger; there being a lesser spot, that they told us, had been heretofore a part thereof, which floated likewise.”
[Philosophical Transactions (London, 1697), 537–8.]
As we see, Halley suggests that the author of the additions to Camden’s work did not believe that the island existed. But this is not completely true. We can be certain that Halley is referring to the 1695 edition of Camden’s work, which had been published two years before Halley visited Eryri. This was a new edition and translation of Camden’s Britannia by Edmund Gibson, who had invited Edward Lhwyd to add to the Welsh parts. Lhwyd is therefore the ‘Author of the Additions to Cambden [sic]’, and his additions are given at the end of each county. Lhwyd doesn’t actually deny the existence of the island, but he seems to have been unimpressed by it and calls it ‘a little green patch’, seeming unsure why people had given it so much attention. He says, after referring to Geraldius Cambrensis’s description:
“The Lake wherein he tells us there’s a wandring Island, is a small pond, call’d Lhyn y Dywarchen, (i.e. Lacus cespitus,) from a little green patch near the brink of it, which is all the occasion of the fable of the wandring Island.”
[W. Camden, Britannia, newly translated … by Edmund Gibson, with annotations to the text (London, 1695), column 669.]
I wonder whether Lhwyd (or his source) actually saw the ‘lesser spot’ which Halley had seen, namely the small piece of the turf that had become detached from the main tywarchen; and did he fail to see the main tywarchen because it was resting against the shore, and therefore appeared to be part of the mainland? In any event, it is clear that Halley felt that Lhwyd had not done justice to the size of the tywarchen.
Thomas Pennant also explored the area in the early 1770s, and it is at this time that he is likely to have seen the lake with a large piece of turf swimming on it. In 1781 he described the scene as follows:
“Llyn y Dywarchen, or The Lake of the Sod … It had on it a floating island, of an irregular shape, and about nine yards long. It appeared to be only a piece of the turbery, undermined by the water, torn off, and kept together by the close entangling of the roots, which form that species of ground. It frequently is set in motion by the wind; often joins its native banks; and, as Giraldus says, cattle are frequently surprized on it, and by another gale carried a short voyage from the shore.”
[Thomas Pennant, A Journey to Snowdon (London, 1781), 180, and also Tours in Wales (1784), ii. 187–8. Thanks to Mary-Ann Constantine for the references.]
The tywarchen or turf doesn’t exist today, but it’s obvious that it was once of quite a considerable size, because it survived from the time of Gerald of Wales towards the end of the twelfth century until modern times – although it’s rather uncertain when it actually disappeared. However it is certain that the tywarchen is not the static island that is in the middle of the island today, as for instance J. Lloyd-Jones claimed in his standard study of Caernarfonshire place-names [J. Lloyd-Joness, Enwau Lleoedd Sir Gaernarfon (Caerdydd, 1928), 91, ‘Llyn y Dywarchen, ger Rhyd-ddu, oddi wrth yr ynys fechan yn ei ganol’ ‘Llyn y Dywarchen, near Rhyd-ddu, so called from the small island in its middle’]. As T.H. Parry-Williams explained:
“Y mae clampen o ynys rugog, greigiog, yn sownd a solet yn ei ganol er pan wyf i’n cofio; ond nid yr ynys hon ydyw’r ‘Dywarchen’ y cyfeirir ati yn ei enw ychwaith. ‘Tywarchen’ ydoedd honno ͏– talp neu ysglisen go helaeth o dir ͏– wedi ymryddhau o’r glannau ac a fyddai’n nofio ar hyd wyneb y llyn at drugaredd y gwynt. Gallai defaid gerdded iddi a phori arni pan ddelai at y lan, ac ar gefn hynny gael gwibdaith yma a thraw hyd y llyn … Gyda llaw, ni welais i erioed y wir dywarchen, i fod yn hollol siŵr. Efallai mai ymddangos yn gyfnodol yn y llyn y bydd hi, fel y bydd planed yn yr wybren.”
There is large rocky island covered in heather and anchored solidly in the middle [of the lake] since I can remember; but this island is not the ‘Tywarchen’ to which the lake’s name refers. That was a ‘turf’ - a large mass or slice of land ͏ – having become detached from the bank and floating along the lake’s surface at the mercy of the wind. Sheep could walk onto it to graze when it came ashore, and subsequently enjoy a trip here and there along the lake … By the way, I never saw the true ‘tywarchen’ to be sure. Perhaps it appears periodically in the lake, as a planet does in the sky.
[T.H. Parry-Williams, O’r Pedwar Gwynt (Dinbych, 1944), 70. The rather literal translation is mine. Thanks to Philip Henry Jones for the reference.]
It seems likely that the turfy island had therefore disappeared by the 1890s, when T.H. Parry Williams was a child. I wonder if the remnants of the island can be seen on the OS Map here, in the bottom right?
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