This is a view of Cassiobury Park, near Watford, from the north-west, at Iron Bridge Lock on the Grand Union Canal. The lower lock gate is in the left foreground and the bridge (actually of brick) is to the right. Turner sketched the same scene on the recto (D12245; Turner Bequest CLV 5; see catalogue note for the subject and related work), but from a few yards nearer the canal and without the figures and horses. For the canal, see note to D12241; Turner Bequest CLV 2.
The inscription, lower left, refers to the original order of the pages. The majority of pages in this sketchbook are similarly inscribed (for the significance of this see notes to D12241, D12244; Turner Bequest CLV 2, 4a). The inscription in this case additionally tells us that at the time when the original schedule of the Bequest was drawn up, one page between this and the original page 12(D12247; Turner Bequest CLV 6) had already been removed [‘cut out’]. This must presumably be identifiable with one of the few leaves that are not inscribed in this manner.