John Constable (1776-1837) is best known for his idyllic paintings of the English countryside. Yet he was also a brilliant innovator who brought a new vivacity to the observation of nature. He practiced oil painting in the open air, capturing in particular the "effervescent" effects of atmospherics--as can be seen, for example, in his wonderful studies of clouds. His art became a benchmark for naturalist painters throughout Europe and America in the...