Giuseppe de Nittis, Vesuvius, 1872.
I find this agreeably matter-of-fact; compare it to this more dramatic representation by our Norwegian friend Johan Christian Dahl:
Joseph Wright of Derby visited Vesuvius in 1774, when the mountain was not at its most active; there was a big eruption later in that decade. He became obsessed with the subject, which suited him very well because he had such a love of dramatic lighting effects, and he made about thirty paintings of it over the years. I am afraid only the last two scans are of adequate quality.
A detail from the previous painting.
A gouache study.