Turner Sketching

My continuing interest in Turner has unearthed a interesting example of how he would sketch, he tended to rely more on his memory and used some of his sketches as reminders in his book on Turner'A Wonderful Range Of Mind' John Gage(Yale Universitey Press 1987) uses the following example which I thought very interesting and wanted to share with you

A young medical student, R.J.Graves,crossed the Alps with the painter, and noticed him useing a notebook, ' across the pages of which his hand, from time to time, passed with the rapiditly of lightining'. in due course graves curiosity got the better of him and he looked over and saw that Turner was recording the passing clouds. Turner's approach to scenery was increasingly to make rapid pencil notations often in the process o travelling, then to flesh some of them out in colour. on the basis of much nore protected observation which were entirely mental.

The above quote was interesting and i have read somewhere else that he did a similiar kind of thing walking round London observing the changing perespective of the city