Both Sotheby’s and Christie’s are holding significant Impressionist and Modern evening sales in London this week. “We’re seeing a very strong market for top quality Impressionist paintings this summer,” the vice chairman of Impressionist & Modern Art Worldwide at Sotheby’s, Helena Newman, said.

On Wednesday, Sotheby’s will put up Monet’s “La Plage à Trouville” expected to fetch between $14 million and $20 million. “It’s an iconic work,” Ms. Newman said. “Monet was exploring the effects of the wind and the light on the water, all quintessentially Impressionist effects.”

Monet completed his painting in 1870 while vacationing with his wife and son at the tony French resort town of Trouville.

A Claude Monet painting of a bridge with two trains passing over the Seine while pleasure boats float below was auctioned Tuesday for more than $41 million, breaking the auction record for the French impressionist artist.

“Le Pont du chemin de fer a Argenteuil” was sold at Christie’s impressionist and modern art sale for $41,481,000, said Rik Pike, a spokesman for the auction house.

The previous record for a Monet painting was $36.5 million for his 1904 “Nympheas,” which was sold last year.

Paintings by some of the world’s most famous artists have been stolen by an armed gang from a museum in Zurich.

Four oil paintings worth more than 112,000,000 Euros by Cezanne, Degas, van Gogh and Monet were taken in the weekend robbery from the E.G. Buehrle museum.

A police statement said three robbers wearing ski masks and dark clothing entered the museum half-an-hour before closing on Sunday. While one of the men used a pistol to force museum personnel to the floor, the other two robbers went into the exhibition hall and collected the four masterpieces.