The first London underground line; the Metropolitan line, opened in 1863. This lithograph shows the line near Paddington in that year. The reality would surely have been more filled with smoke.

Translators note:

Some of the problems that I have encountered are:
The author uses filler words, almost asides, for example 'erchyll ydyw' it is dreadful.
He talks of a 'great crowd' in line 2 - I've put 'so many' because it sounds better but you can change it.
He uses words in a strange way - 'gwiwlan' means holy, worthy, pure, right-living, amiable, fair or beautiful', but he writes 'yn hoff wiwlan aent i ffwrdd - they set off fondly/amiably + (g)wiwlan. Similarly there's a novel way of using the word 'gwiw' in 'wiwber' and 'wiwlon'.
He states that the young man (verse 15) was lost 'unconcealed' - I've put 'evidently'. Also, the last line of this verse translates literally as 'and after him the young girl is precisely day and night with a sad breast', so I've used a bit of 'translator's licence'.
'Cyfeillion' and 'ffrindiau' both mean 'friends' but in order to avoid repeating the word 'friends', I used another word for 'cyfeillion', 'fellows'
There's part of a word missing from the second line of verse 6; it begins with tr and ends with en. I think this word is 'truan' - 'wretched'

Eirionedd Baskerville

The Rothsay Castle was built on the Clyde in 1816 as a river boat. (See bar708~On the Rothsay Castle Steam-Boat and also bar666~Clyde Steamers 1818)

She was moved to Liverpool where she was used for day trips along the coast of North Wales; a task for which she was too small and, by 1831, too old. At around midday on August 17, 1831, she left the Mersey carrying 150 passengers and soon met strong wind and rough sea. A passenger asked Captain Atkinson, to return to port, but Atkinson was drunk and refused to go back. By 10 p.m. there were two feet (61 cm) of water in the stokehold. The pumps did not to work; the single lifeboat had a hole in the bottom; and there was no signalling apparatus to attract help. At around 1 a.m. on August 18th the Rothsay Castle ran aground and broke up. The captain and the two mates were swept to their death when the funnel collapsed. Only 23 passengers were rescued; 130 passengers and crew were lost. The coroner's jury concluded: "had the Rothsay Castle been a seaworthy vessel and properly manned, this awful calamity might have been averted. They therefore cannot disguise their indignation at the conduct of those who could place such a vessel on this station (i) Bodies were washed up over a wide area of Anglesey and the Welsh mainland. In 1832 the Reverend William Williams won the prize for poetry at the Eisteddfod in Beaumaris for a poem telling the story of the disaster. (ii)

References:
(i) http://en.wikipedia.org/wiki/Rothsay_Castle_(ship)]
(ii) http://www.museumwales.ac.uk/en/313/