In 1846, Darwin rented from Sir John William Lubbock a narrow strip of land of adjoining the Down House grounds to the southwest, and had it planted. He named it the Sandwalk Wood. One side was shaded by an old shaw with oak trees, and the other looked over a hedge to a charming valley. Darwin had a variety of trees planted, and ordered a gravel path known as the "sandwalk" to be created around the perimeter. Darwin's daily walk of several circuits of this path served both for exercise and for uninterrupted thinking. He set up a number of small stones at one point on the walk so that he could kick a stone to the side each time he passed, so that he did not have to interrupt his thoughts by consciously counting the number of circuits he had made that day. The sandwalk also served as a playground for his children. A wooden summerhouse was built at the lower end of the sandwalk. In 1874, Darwin gave a piece of pasture land to Sir John Lubbock (the son) in exchange for ownership of the Sandwalk Wood. From 1849, Darwin used it to continue his walking exercise on return from Dr. Gully's hydrotherapy treatment.