This is "A Wagon in the Plains of Artois" by Jean-Baptiste-Camille Corot. Painted in 1871, it's one of a series of works created during his stay in north-east France that spring and summer. If you look at the horizon just right of centre, you'll see a windmill, its sails visible against the sky - windmills were a common sight here back then.
In the foreground, we have a horse with its head bowed, and the wagon from which this painting takes its name. Notice how Corot has used different techniques to create depth and texture in this piece. He's added a layer of grey over the original canvas preparation, leaving some areas exposed, especially in the sky where it creates dark tones for the clouds.
The sky itself is painted with a thick blue mixed with white, using long strokes that follow the horizon line. You can still see the ghostly forms of trees beneath the paint. It's a beautiful example of Corot's ability to capture the natural world on canvas.
A Wagon in the Plains of Artois hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.