Grand and Royal canals
Several pages into Hades, the funeral carriages cross "The grand canal" at Victoria Bridge. Later in the chapter, they pass over the "Crossguns bridge: the royal canal." These two canals connect Dublin to the west of Ireland by way of the River Shannon.
The Grand Canal and its northern twin the Royal Canal were constructed in the second half of the 18th century and the first two decades of the 19th, to connect Dublin to the Shannon in central Ireland. Their long curving arms encircle central Dublin, ending near the Liffey on the eastern edge of the city. Each canal is 80-90 miles long (130-150 kilometers), with many locks. As he crosses the Crossguns bridge, Bloom thinks of "Dropping down lock by lock to Dublin. With turf from the midland bogs."
The Crossguns bridge—officially named Westmoreland Bridge
when it was built, but the name didn't stick—carries "Phibsborough
Road" over the Royal Canal, leaving metropolitan Dublin
for the northern suburbs in an area long known as Crossguns.
Underneath the bridge is a lock allowing canal barges to be
lowered from the landward (western) level to the lower level
that is maintained to the east. As the funeral carriages pass
over the bridge, their occupants can see that the lock is
currently in use: "Water rushed roaring through the
sluices. A man stood on his dropping barge, between clamps
of turf. On the towpath by the lock a slacktethered horse."
Several hours later, in Wandering Rocks, Father Conmee
sees the same barge "Moored under the trees of Charleville
Mall," about a mile farther east on the Royal Canal near
the crossing of the North Strand Road.
Bloom thinks that the canal goes through Mullingar, and he
could visit his daughter by walking or cycling along it. He
thinks also of the foul condition of the water in the canals:
"slime, mudchoked bottles, carrion dogs." In
Ithaca he thinks of the dire "possibility of recourse
being had to the impotable water of the Grand and Royal
canals as in 1893," Dublin currently being in the
grip of a drought.
Near the end of Wandering Rocks the viceregal
cavalcade proceeds down Lower Mount Street, and then the
narrative mentions an advertisement posted near "the Royal
Canal bridge." This must have been a slip on Joyce's
part, because Mount Street Lower heads southeast from Merrion
Square and crosses the Grand Canal before becoming
Molly mentions canals several times in Penelope,
without naming them. She remembers that in 1893 "the canal
was frozen." This must have been the Grand Canal: the
canals did freeze over in February 1893, and in Hades
Bloom remembers Rudy having been conceived in March or April
of that year "in Raymond Terrace," which lies only a few
blocks away. Molly also remembers having kissed Lieutenant
Stanley Gardner goodbye "at the canal lock" as he was
about to leave for South Africa.