Attention was first drawn to the Flat Rocks gallery by the late R. H. Mathews, who illustrated nine of the figures in various papers between 1895 and 1899. He visited the site (Group 6) during his work as a surveyor and had it reserved as a national monument. In 1945 Mr. Gordon Boes gave me the localities of Groups 1 to 5 on the same ridge, which runs from the south-west to the north-east for about ten miles, extending from Gunderman, on the Hawkesbury River, to Mangrove Creek. I first visited Flat Rocks in 1947 with Mr. Paddy Pallin, and in the same year I spent a week recording Groups 1 to 7, in the area between Starkey Trigonometrical Station and Flat Rocks, accompanied by Mr. R. Gavin, a Museum preparator. I spent a week in early April, 1954, accompanied by another preparator, Mr. N. Camps, recording Groups 8 to 13 which are situated east of Flat Rocks and on a ridge some distance away. Flat Rocks ridge is situated in typical Hawkesbury sandstone country covered with eucalypt open forest or woodland. The undergrowth is patchy on the ridges but is often thick and spiky in the gorge and valley bottoms. On the ridges the terrain is rough, being covered with broken rocks and large outcrops of sandstone. The trees push up rings of rocks at their base as they develop to maturity, and when the trees are burnt out by a bush fire these rings of stones suggest artificial arrangements.