THE RIVER SCENERY AT THE HEAD OF THE VALE OF NEATH. By F. J. NORTH, D.Sc., F.G.S. Introduction-Position and extent of area to be described- The development of a river system-The geological structure of the district-The valleys, on the outcrop of the Old Red Sandstone-The valleys, on the outcrop of the Carboniferous Limestone-Underground water courses-The valleys, on the outcrops of the Millstone Grit and the Coal Measures-Water- falls, their nature and origin-The waterfalls of the Vale of Neath "-Conclusion. When nimble Nedd To all the neighbouring nymphs for her rare beauties known, Besides her double head to help her stream, that hath Her handmaids, Melta, sweet clear Hepsy and Tragarth, From Brecon forth doth break." Michael Drayton in Poly-olbion (1622). Introduction.-Oft referred to, yet seldom enjoyed by the majority of those whose homes are within easy reach, the beauties of the country drained by the head-waters. of the River Neath have long been recognised even in the early part of the seventeenth century, when travel was neither easy nor expeditious, Michael Drayton knew and appreciated the district sufficiently well to mention by name, not only the Mellte and the Hepste, but also the Dringarth-only about five miles long-in the remarkable description of the beauties of England and Wales to which he gave the name Poly-olbion.* In the same century the district was visited by Edward Lhuyd-naturalist, antiquary, and Keeper of the Ashmolean Museum in the time of William III. In a letter to John Ray (1698), contributing to the controversy then raging concerning the origin of fossils, he wrote On the sides as well as the bottom of a noted cave called Porth Gogo, at Ystrad Velhte in Brecknockshire, I Poly-olbion, or a Chorographicall Description of all the Tracts, Rivers, Mountaines, Forests, and other Parts of Great Britaine," 1622.