The Cambrian Mts. cover most of Wales, with high points at Snowdon (3,560 ft/1,085 m), Plynlimon (2,468 ft/752 m), and Cader Idris (2,970 ft/905 m). The eastern rivers-the Dee, Severn, and Wye-drain into England. The Usk flows through Monmouthshire into the Bristol Channel. The Towy, Teifi, Taff, Dovey, and Conway rivers lie completely in Wales. The eastern boundary, drawn in 1536, united England and Wales politically but disregarded cultural and linguistic distribution. Welsh-speaking areas were added to England's Herefordshire, Shropshire, and Gloucestershire; the language survived in Herefordshire until the 18th cent. and survives to a small extent in Shropshire today. Wales has maintained a distinctive culture despite its long union with England. Wales comprises eight counties: Clwyd, Dyfed, Gwent, Gwynedd, Mid Glamorgan, Powys, South Glamorgan, and West Glamorgan. In the 1990s about 25% of the population spoke Welsh, although in certain regions the percentage was much higher. The Univ. of Wales was created in 1893 by royal charter; it is the collective name of four constituent colleges-three of them created before the incorporation-at Aberystwyth (1872), Cardiff (1883), Bangor (1884), and Swansea (1920); the national school of medicine is also in the system.