Barton swing bridge and aqueduct.

Two bridges were built at Barton, one to carry the road over the canal and the other to carry the Bridgewater canal  -  the aqueduct being justifiably considered as one of the wonders of the waterway.

When the ship canal was being built one of the greatest challenges facing the builders was how to arrange for the heavy Bridgewater canal  traffic to cross the new canal.   The Bridgewater was being carried over the Irwell at this point by the original, three arched stone aqueduct built by James Brindley in 1761 which had been designed to allow the "Mersey Flats" to pass along the river into the centre of Manchester.   Clearly the original bridge was no longer acceptable and various designs were put forward as to how the Bridgewater traffic could be taken over the ship canal.

Amongst the proposals were the construction of two boat lifts, similar to the Anderson Lift between the Trent and Mersey Canal and the Weaver Navigation,  and a double flight of locks - one on each side of the ship canal. Both schemes required the Bridgewater traffic to be lowered to the ship canal for the short transit across, and then to be lifted back up to the original level to continue their journey - clearly a time consuming and expensive process.  The final solution was to build a swing aqueduct, a great engineering feat, and one which had never been attempted before.

Both the road bridge and the aqueduct are built to turn on the same central pier, with the road bridge being slightly  downstream of the aqueduct.

The road bridge carries a very busy  road and is constructed in the same manner to all the other swing bridges along the canal with the deck of the bridge resting on an annular girder some 31 feet in diameter, and with a central pivot and a roller path on which to turn. Sunk into the concrete base in the supporting pier is a lower roller containing approximately   64 cast iron rollers. A toothed rack is bolted to the annular girder and this is set in motion to move the bridge by the use of hydraulic pinions.  Gates are provided at each end of the bridge to control the road traffic. This is the only swing bridge (apart from the aqueduct) to be supported on a central pier built in the canal, all others are pivoted at one end or the other.

The aqueduct works in similar way to the road bridge in that the whole structure is turned on a table of 64 rollers but in this case it is partly supported centrally by a powerful hydraulic ram which can be forced upwards to offset half the weight of the bridge.  Again the motive power is hydraulic with 2 pinions engaging on a toothed rack bolted to the annular ring. A hydraulic buffer and a locking bolt keep the bridge securely fixed when aqueduct closed.

When the bridge swings to allow traffic on the ship canal to pass the swinging tank of the aqueduct and the joining ends of the Bridgewater canal are sealed with hinged doors closed by hydraulic rams.

Between each end of the tank and the junctions with the  canal there  is a U shaped piece of iron some 12 inches thick which is shod with rubber on both sides, this fits the exact shape of canal and forms a seal.  Once the doors are closed and water is sealed in the tank and the canal,  these pieces are slid out hydraulically to leave sufficient gap to allow the tank to be swung. Once the bridge is closed and back in line with the Bridgewater canal these pieces are slid back in to seal all the gaps before the sealing doors are opened again.

The total weight of the aqueduct when full of water is some 1,450 tons, this includes 800 tons of Bridgewater canal water contained in a tank 235 feet long by 19 feet wide and 6 feet deep. The  towpath (now blocked off) was constructed some feet higher up the structure in order  to reduce the total width of the aqueduct and so minimise the construction costs.

Brindleys original aqueduct was situated between the two bridges and traces of it can still be seen on the Eccles side of the canal.

The aqueduct is in operation between 09:15 and 16:30 daily during the winter months and between 09:15 (Mon-Thurs) and from 09:15 until 20:30 (Fri-Sun) during the summer. The aqueduct is always swung into the open position outside these times in order to allow ship canal traffic to pass when the bridge is not manned.