The main feature of the Island is the range of chalk downs running east and west, and terminating in the bold cliffs of white chalk at Freshwater and the Culvers. Here we have vertical cliffs of great height, their white softened to grey by weathering and the soft haze through which they are often seen. In striking contrast of colour are the Red Cliff of Lower Greensand adjoining the Culvers, and the many-coloured sands of Alum Bay joining on to the chalk of Freshwater. The summits of the chalk downs have a characteristic softly rounded form, and the chalk is covered with close short herbage suited to the sheep which frequently dot the green surface. Where sheets of flint gravel cap the downs, as on St. Boniface, they are covered by furze and heather, producing a charming variation from the smooth turf where the surface is chalk. The Lower Greensand forms most of the undulating country between the two ranges of downs; while the Upper Greensand, though occupying a smaller area, produces one of the most conspicuous features of the scenery--the walls of escarpment that form the inland cliffs between Shanklin and Wroxall, Gat Cliff above Appuldurcombe, the fine wall of Gore Cliff above Rocken End, and the line of cliffs above the Undercliff. To the Gault Clay is due the formation of the Undercliff--the terrace of tumbled strata running for miles well above the sea, but sheltered by an upper cliff on the north, and in parts overgrown with picturesque woods. The impervious Gault clay throws out springs around the downs, which form the headwaters of the various Island streams. The upper division of the Lower Greensand, the Sandrock, forms picturesque undulating foothills, often wooded, as at Apsecastle, and at Appuldurcombe and Godshill Park. On a spur of the Sandrock stands Godshill Church, a landmark visible for miles around. At Atherfield we have a fine line of cliffs of Lower Greensand, while the Wealden Strata on to Brook form lower and softer cliffs. To the north of the central downs the Tertiary sands and clays, often covered by Plateau gravel, form an extended slope towards the Solent shore, much of it well wooded, and presenting a charming landscape seen from the tops of the downs. This slope of Tertiary strata is deeply cut into by streams, which form ravines and picturesque creeks, as Wootton Creek, 200 feet below the level of the surrounding country. While much of the Island coast is a line of vertical cliff, the northern shores are of gentler aspect, wooded slopes reaching to the water's edge, or meadow land sloping gradually to the sea level. Opposite the mouths of streams are banks of shingle and sand dunes, forming the spits locally known as "dovers." Some of these, in particular, St. Helen's Spit, afford interesting hunting grounds for the botanist.