Page 258. " on the day of Gambetta's funeral "

Léon Gambetta by Léon Bonnat
Public DomainLéon Gambetta by Léon Bonnat
Léon Gambetta (1838-1882) was a French statesman who became prominent after the Franco-Prussian War (see bookmark to p. 104, "I can remember them in '70"). He died on 31st December 1882, so his funeral was presumably early in January 1883; but Proust plays a bit fast and loose with dates in the Search so this does not necessarily provide a particularly useful signpost in time. 

Page 266. " her devotion to Our Lady of Laghet "

Our Lady of Laghet is a place of pilgrimage in France, near Monaco. This corresponds with the time Odette spent in nearby Nice.

Page 267. " her resemblance to the figure of Zipporah, Jethro's daughter "
Botticelli's Zipporah
Public DomainBotticelli's Zipporah
In Exodus, Moses's wife Zipporah saves his life by circumcising their son, which Moses had incurred God's wrath by failing to do. The fresco of Moses and Zipporah in the Sistine Chapel is by Alessandro di Mariano di Vanni Filipepi, better known, as the narrator says, as Sandro Botticelli ('little barrel') (1445-1510).

Confusingly, there are two Zipporahs in the Sistine Chapel. The other is by Pietro Perugino (1446–1524).

Page 267. " a bust of the Doge Loredan by Antonio Rizzo "

Antonio Rizzo (c.1440-1499) was a minor Early Renaissance sculptor. A more famous portrait of the Doge of Venice, Leonardo Loredan (1436-1521) by Bellini is in the National Gallery in London.

Page 267. " in the colouring of a Ghirlandaio "

Ghirlandaio's Francesco Sassetti and his Son
Public DomainGhirlandaio's Francesco Sassetti and his Son
Domenico Ghirlandaio (1449-1494) was an Italian Renaissance painter from Florence, whose apprentices included Michelangelo. Most of Swann's points of comparison are with Italian Renaissance painting and sculpture.

Page 267. " in a portrait by Tintoretto "

Jacopo Comin, known as Tintoretto (1518-1594) was a Venetian painter from the late Renaissance period. 

Tintoretto, Self Portrait as a Young Man
Public DomainTintoretto, Self Portrait as a Young Man

Page 271. " the day of the Paris-Murcie Fête given for the victims of the recent floods in Murcia "

On October 14th 1879 a thunderstorm caused extensive flooding in the Spanish region of Murcia. More than 5,000 people had to flee their homes, losing everything they owned, and over 150 died. The disaster was widely reported in the press at the time, resulting in many fundraising efforts, such as mentioned here.

Murcia is still prone to flooding. In 2009 a 25-year-old woman drowned in her car during a bad storm which had already claimed two lives.