This is where the output of the Llanberis (Padarn) slate quarries was transhipped to vessels or to the L&NW Railway. A gas works with two holders was built on the corner of the sea wall, southwest of the dock, presumably to help extend the hours during which transhipment could take place. Whether the many terraced houses were also supplied is not known, nor whether the main road (Bangor Street, later the A487) was ever lighted by gas. The gas works appears identically on the Ordnance Surveys of 1888 and 1899 but the 1913 revision does not show the gasholders. (Either the gas supply had been discontinued or the sheet was censored because of wartime publication). A single Chimney made from sawn blocks of slate survives on the site on a road called Hen Gei Llechi, Cadw Listed building refer to the chimney as the Gasworks Chimney which is listed and still stands. The gasworks were visible on the 1888 to 1959 OS maps.