When a lock is filling, the bottom of the lock is filled from the pond, and the rest is drawn from the upper pound. Typically, this system uses 40 per cent less water, but the ponds have been disused for a long time, and an electric pump is now used to pump water from the bottom of the flight to the top. The Grand Junction Canal experimented with side ponds from the early 1800s. The locks at Bourne End had several radial ponds, but use of the ponds was abandoned because it took too long to use the lock. Those at Buckby had two rectangular side ponds per lock, at different levels, and this design was eventually installed at most locks between Buckby and lock 45 at Bulbourne, the junction with the Wendover Arm. Location The locks are numbered from 7 at the top of the flight to 13 at the bottom. To the south of the flight is a long level pound, which stretches to the Stoke Bruerne Canal Museum and the top of the Stoke Bruerne flight of seven locks. Towards the southern end of this section is Blisworth Tunnel and Gayton Junction, where the Northampton Branch turns off to join the River Nene at Northampton. Just below the junction, the railway line from London to Rugby crosses the canal and then runs parallel to it. About below Whilton Locks, the M1 motorway approaches, and runs along the east bank, so that the bottom four locks are sandwiched between the railway and the motorway. The railway then crosses to the east bank, and the canal diverges to the west. Just before the final lock, the canal passes under Watling Street, once a Roman road and now part of the A5 road. The Leicester section of the Grand Union Canal then turns off at Norton Junction, and the canal continues on the level, passing through Braunston Tunnel to reach the top lock of the six that descend to Braunston, from the top of the Whilton flight. The canal is above sea level at the top of the flight, and the locks drop the level by to . Whilton Marina is located close to the bottom lock. It was set up in 1971 in a field beside the canal, and now has 200 private moorings, while another 50 are occupied by boats which are for sale. The marina offers a