THE Barrier Ranges, in which the Broken Hill mines occur, are situated just within the western boundary of New South Wales. The country-more especially the southern portion- may be described generally as undulating, but broken at intervals by rough ridges consisting of the harder rocks.Towards the north the ranges increase in height and roughness. The principal rocks forming the Barrier Ranges proper are metamorphic crystalline schists, represented by gneiss, mica-schists and the usual associated rocks, of various composition and structure, enclosing granitic and dioritic veins and dykes (and probably intercalated or overflow sheets of the latter rock), varying from a few inches to several hundred feet in width. The southern portion of this belt of rocks has a width of about 26 miles, gradually decreasing to about 10 or 12 miles at the northern end. The total length is about 80 miles, and the strike is approximately N.E. and S.W., becoming almost N. and S. towards the northern end.