The Thames forms the county boundary at Old Windsor from a point a little above Magna Charta Island and separates Berkshire from Buckinghamshire, and later on from Oxfordshire, the boundary sometimes running in midstream, sometimes on one bank, and sometimes on the other bank. Near Oxford the boundary passes for a short distance a little to the west of the river, that is on the Berks side. The Upper Thames or Isis becomes the boundary between Berkshire and Oxfordshire, and then for a very short distance between Berkshire and Gloucestershire, until near Buscot the river Cole joins the Isis and the boundary turns in a southerly direction near to the bank of the Cole, the adjoining county being then Wiltshire. The county boundary runs by or close to the river Cole to near Bourton, and it then crosses the chalk country with no definite marks. At one point it crosses an old earthwork, Membury Fort, and reaches the river Kennet a little east of Chilton Foliat. From this point to near Woodhay, a distance of some 14 miles, the boundary of the county for administrative purposes differs from the boundary of the ancient or geographical county (see page 9), indeed considerable alterations have been made in this part of the county boundary at various times. The present administrative boundary after crossing the Kennet, turns in a westerly and then in a south-easterly direction following the border of Hungerford and Inkpen parishes and runs on to a point at the south-western corner of Combe parish where Berkshire, Wiltshire, and Hampshire meet. The Berkshire boundary then runs west to Pilot Hill and then turning takes a northerly or north-easterly course until it reaches the stream Emborne which it follows for several miles until near Brimpton the stream bends sharply northwards to join the river Kennet, while the county boundary continues its easterly course through a forest country to the Imp Stone plantation. It then makes a wide detour to the north leaving Mortimer West End and the Roman town of Silchester in Hampshire. This part of the boundary has at more than one date been subject to alteration and for a time it ran close to Silchester and is thus marked on many maps. Stratfield Mortimer is in Berkshire, and about a mile to the east of Silchester the county boundary reaches a Roman road which it follows pretty closely for a considerable distance, crossing the river Loddon at Stamford End Mill. On the east of the Loddon we come to a small tract which, until modern times, was an outlying part of Wiltshire, bounded in part by Berkshire and in part by Hampshire. It is now included in the former county, and the Berkshire boundary continues its easterly direction on or near the Roman road until it reaches the stream Whitewater close to its junction with the Blackwater. The county boundary reaches the latter river close to a ford, no doubt a well-known place, for these fords are in most cases very old crossing-places and this one certainly goes