In the preface to The Harbours of England (1858), Ruskin explains that each of Turner's designs 'should be considered as expressing part of a continuous system of thought'. This resulted in the commencement of 'many series of drawings... under titles representing rather the relation which the executed designs bore to the materials accumulated in his own mind, than the position which they could justifiably claim when contemplated by others'. In consequence, Ruskin points out, The Rivers of England 'was closed without a single drawing of a rapidly running stream'; and the engravings for The Rivers of France were assembled 'without including a single illustration either of the Rhone or the Garonne' ( Works, 13.9).
Ruskin 's conception of the coherence of such systems of thought in Turner 's work is particularly well-illustrated by his writings concerning the Liber Studiorum.