THE Peaks silver field is situated at the head of Burragorang Valley, in parish of The Peaks, county of Westmoreland, New South Wales. The Tonalli River (a tributary of the Wollondilly River), with its associated creeks, drains the main portion of the area. A.-TOPOGRAPHY. The country in which the lodes occur consists of steep hills composed of quartz-felsite. These are surrounded by high vertical escarpments of sedimentary rocks of Permo-Carboniferous and Triassic age which no doubt at one time covered the whole district, but have now been removed from very considerable areas by denudation, thereby leaving the felsite boss, with its contained lodes, exposed at the surface. The region undoubtedly represents a highly dissected plateau, the great ridges and isolated peaks bearing testimony to the cycles of erosion through which the old upland has passed, finally resulting in the bringing about of the present topography.