he perfected his style. His landscapes are sunnier than the equivalent scenes by Jacob van Ruisdael, with the principal trees typically seen with sky behind. His skill at varying effects of light and colour throughout a work is exceptional. He often makes use of double vanishing points to add interest to the composition. Some of his compositions, as late as 1664, are near-copies of Jacob van Ruysdael, and he often repeats his own compositions with variations; four of the five works in the Wallace Collection have other versions. For some of these he made use of assistants, though little is known about them or their role. His paths or roads normally wind diagonally across his composition through dense trees and vegetation, the trees spreading and varying in size. The water mills and other buildings are generally seen in the near distance, and generally only one or two appear in each picture. His compositions are carefully contrived and presumably imaginary, normally avoiding all symmetry. The Avenue at Middelharnis, a very late work, is a surprising break from most of these somewhat "tired conventions of his earlier work", and a very accurate depiction of a specific spot. In contrast to his usual scenes of rough woodland, in this scene the straight lines, lopped trees, deep drainage ditches on both sides of the road, and regimented young trees in the plot to the right, all emphasize the man-made nature of this landscape. A patch of rough woodland remains in the left foreground, contrasting with the saplings in rows on the right. The man tending to these is unusual in 17th-century Dutch landscapes, which rarely show anyone working the land. The Haarlem Lock, Amsterdam in the National Gallery is his only generally accepted townscape, and still shows a foreground mainly of trees and water. The corner of the street where Hobbema was living by 1668 can be seen at the left. In some cases he delegated the human figures in his paintings to Adriaen van de Velde and perhaps others, a common practice in the period. In others he did the figures but probably sub-contracted birds and animals. He often painted on oak panels, at least to the late 1660s; of the nine paintings in the National Gallery, five are on oak, but not the two dated 1689. No drawings certainly by him survive, and only a few are attributed. Despite this, it is