"Kish" refers, several times in the novel, to the Kish Bank, a dangerous sandbar approximately 7 miles east of Dublin with a long history of wrecking oceangoing vessels. The shoals now have a lighthouse, but in 1904 a "lightship" was moored there, supplied and manned (as the lighthouse is today) by the "Irish lights" board, a government agency charged with maritime safety.
In Proteus Stephen asks himself, "Here, I am not walking out to the Kish lightship, am I?" In Nausicaa, Bloom reclines on the same Sandymount beach and sees a light far out on the waves: "And far on Kish bank the anchored lightship twinkled, winked at Mr Bloom." Such lightships (still to be found in Ireland and the UK) warned pilots of navigation hazards at sites where it would be impossible or prohibitively expensive to build a lighthouse. They had large letters on their sides, announcing not the name of the vessel but its location. A stout mast or superstructure supported a single light high enough off the water to be visible from passing ships.
Men were needed to staff these lonely outposts, a fact that arouses Bloom's sympathy in Nausicaa: "Life those chaps out there must have, stuck in the same spot." He remembers the crew of the Erin's King "throwing them the sack of old papers," a frail lifeline to civilization.
This memory, first recalled in Calypso, comes from a time when Bloom took his daughter Milly "On the Erin's King that day round the Kish." Gifford notes that it was "an excursion steamer that took sightseers on two-hour trips around Dublin Bay, circling the Kish lightship to the south or Ireland's Eye, an island just north of the Howth peninsula, to the north. During the summer it sailed several times a day from Custom House Quay in central Dublin; fare, one shilling."
Bloom remembers the "Damned old tub pitching about," but Milly did not suffer the fate of those "lovely seaside girls," seasickness. In Nausicaa he remembers how her spirits contrasted with those of the adults on the ship: "Drunkards out to shake up their livers. Puking overboard to feed the herrings. Nausea. And the women, fear of God in their faces. Milly, no sign of funk. Her blue scarf loose, laughing. Don't know what death is at that age." The memory comes back one last time in Eumaeus: "the Irish lights, Kish and others, liable to capsize at any moment, rounding which he once with his daughter had experienced some remarkably choppy, not to say stormy, weather."
The Irish Lights, mentioned both here and in the Nausicaa passage, was a board of commissioners with regulatory authority over all the lighthouses, lightships, and navigation buoys placed around the coasts of Ireland.