Navigation
Cambridge had been an inland port due to its location on the River Cam prior to the draining of the Fens. As the university colleges rose in importance, the course of the river through the town, known as the Backs, was moved further to the east to accommodate their new buildings. A report conducted in 1618 by Richard Atkyns highlighted the problems caused by sandbanks above Clayhithe and watermills obstructing navigation. An order made by the parliamentary Committee of the Association in 1643 regulated use of the river for trade, but the biggest change was the construction of Denver Sluice on the River Great Ouse, which reduced river levels on the lower river as tidal waters were excluded from the Ouse. Both the university and the Corporation of Cambridge complained to parliament in 1697 that the trade route to the town from King's Lynn had been severely impaired.
In 1699, the Corporation sought to obtain an Act of Parliament which would allow them to improve the river from Clayhithe to Queens Mill at Cambridge. This was obtained on 27 February 1702 and created the Conservators of the River Cam, a legal body with authority to charge tolls for use of the river, which ranged from four shillings (20p) a ton for wine to one penny (0.4p) per person for passengers. The Conservators, of which there were a maximum of eleven, had powers to mortgage the tolls, in order to raise capital for improvements to the river immediately. This they did, and built sluices at Jesus Green, Chesterton, Baits Bite and Clayhithe. Most of the tolls were collected at Clayhithe.
Prior to 1722, Denver sluice had been destroyed, and although Cambridge Corporation opposed its reconstruction, it was rebuilt by 1750. The river entered a period of steady profitability, with toll receipts rising from £432 in 1752 to over £1,000 by 1803. In 1835 they peaked at £1,995, and then declined slightly until 1846. The Convervators also raised some revenue from rents on the public houses which they owned adjacent to each of the sluices. Another Act of Parliament was obtained on 21 July 1813 which allowed the Conservators to alter the tolls and charge penalties, while the South Level Act of 1827 created Commissioners who had responsibility for the river below Bottisham. This act also appointed the vice-chancellor of the university and the mayor as navigation commissioners. The Conservators built locks at Baits Bite and Bottisham, and removed the sluice at Chesterton.
The river was sufficiently profitable that the Conservators were able to contribute £400 towards the cost of rebuilding the Great Bridge, now called the Magdalene Bridge,map 9 in 1823, and a further £300 for the rebuilding of the Small Bridge, now Silver Street Bridge, in 1841. A year later they constructed a house at Clayhithe, which cost £880, and included a large room for meetings and banquets. Just three years later the Eastern Counties Railway reached Cambridge, and the navigation declined rapidly. Receipts dropped from £1,393 in 1846 to £367 in 1850, and were just £99 in 1898. Most commercial carrying on the river had stopped by World War I, although Banhams operated two steam tugs and three barges until the late 1930s, carrying gas water from Cambridge Gasworks to King's Lynn, where it was used in the manufacture of fertiliser. The last recorded passenger services had ceased nearly 100 years earlier, in 1839 and were started again in 2008 with the passenger vessel moored on Jesus Green.
Traffic using the river today consists of private cruisers making the journey to Jesus Lock, with the section above Baits Bite lock regularly in use by the University rowing clubs, both for practice and for races. Motorised craft can navigate along the Backs in winter, but headroom is severely restricted. The Conservators of the River Cam now have an office in the former lock-keepers cottage at Baits Bite, while the house at Clayhithe is now the residence of the foreman of the Conservators. The Conservators are still responsible for the river above Bottisham lock, while the lower river has been managed by the Environment Agency since its creation in 1995.
The three locks are all of different sizes. Bottisham and Baits Bite locks are both fully automated, with a vertical guillotine gate at the upstream end and traditional mitre gates at the downstream end. Jesus lock is manually operated, and has mitre gates at both ends. Boat sizes are restricted to 96.8 ft (29.5 m) by the length of Bottisham lock, and to 14 ft (4.3 m) by the width of Baits Bite lock. Jesus lock is only 9.7 ft (3.0 m) wide. The navigable lodes of Reach, Swaffham Bulbeck and Bottisham, the last of which is no longer navigable, can be reached from the River Cam.
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