From Wikipidia: Turner's talent was recognised early in his life. Financial independence allowed Turner to innovate freely; his mature work is characterised by a chromatic palette and broadly applied atmospheric washes of paint. Suitable vehicles for Turner's imagination were to be found in the subjects of shipwrecks, fires (such as the burning of Parliament in 1834, an event which Turner rushed to witness first-hand, and which he transcribed in a series of watercolour sketches), natural catastrophes, and natural phenomena such as sunlight, storm, rain, and fog. Turner placed human beings in many of his paintings to indicate his affection for humanity on the one hand (note the frequent scenes of people drinking and merry-making or working in the foreground), but its vulnerability and vulgarity amid the 'sublime' nature of the world on the other hand. 'Sublime' here means awe-inspiring, savage grandeur, a natural world unmastered by man, evidence of the power of God–a theme that artists and poets were exploring in this period. The significance of light was to Turner the emanation of God's spirit and this was why he refined the subject matter of his later paintings by leaving out solid objects and detail, concentrating on the play of light on water, the radiance of skies and fires. Although these late paintings appear to be 'impressionistic' and therefore a forerunner of the French school, Turner was striving for expression of spirituality in the world, rather than responding primarily to optical phenomena. In his later years he used oils ever more transparently, and turned to an evocation of almost pure light by use of shimmering colour.
See the videos here: http://www.painters-online.co.uk/open/?page=Turner%20Films