What was the technological development which made British canals possible? Water supply from reservoirs is one possibility, but the real break-through was something far less obvious. To most people, the Duke of Bridgewater's Canal was the one which set the trend for inland navigation in Britain. However, this is to ignore the important northern river navigations built in the early eighteenth century. The Aire & Calder, the Don, the Mersey & Irwell, the Weaver and the Douglas were all built by merchants who wanted to improve their trade, much the same reason as Bridgewater later had for his later canal. They had all opened before planning started on the Bridgewater Canal, and were already proving the worth of inland water transport to new and expanding industries - and to the merchants who owned them.
The economics and technology of canal building can be very different to those of river navigations. To keep the cost of a canal within economic limits it is necessary for the engineer to keep the number of locks to a minimum. On a river navigation, their number and position is dictated by existing mills and the geography of the river. They were restricted in both number and fall, the latter usually being around five feet. To make a canal lock economically, the fall needs to be double this figure. Locks were an expensive item for canal promoters, and the larger fall allowed the number of locks to be kept to a minimum. It was certainly more expensive to build two shallow locks than a single deep one.
With the smaller fall found on locks on river navigations it would have been possible to use gate paddles at either end of the lock. However, if upper gate paddles were used on one of the deeper canal locks they would tend to flood a boat in the lock. How did they get round this problem and enable canals to be built across the country? The answer seems simple today - it was the humble ground paddle.
Ground paddles were first used in the British Isles by Thomas Steers during construction of the Newry Canal around 1740. He fitted them to three locks, contemporary accounts describing them as After the French pattern.
One of the Newry locks about twenty years ago.
The previous century the French had built several canals which crossed country similar to that over which canals were later built in Britain. All the technical problems had been solved there during the construction of the Canal du Midi, and this is the reason why this canal has become a World Heritage Site. However, ground paddles were probably introduced on the Canal de Briare which was built some thirty years earlier, around 1650. Most locks on this canal were rebuilt around 1870 when many French canals were rebuilt to the Freycinet 'peniche' standard. However, the seven-rise flight of locks at Rogny were by-passed. They survive today as a national monument, and are fitted with ground paddles. It is a pity the gates have not survived.
So it seems that it was the introduction of the ground paddle which made the typical cross-country British canal possible. In fact, if we look at early drawings of British canal locks, they all show top gates without gate paddles, ground paddles being relied upon for filling the lock. The question then arises as to when were top gate paddles installed. Research is certainly needed into this question, but the date can certainly be idenjpgied on the Leeds & Liverpool Canal. One of the directors, Warde-Aldam, kept notes of discussion at committee meetings, and in 1873 he writes, Jack cloughs (the L&L name for gate paddles) are also to be put in every lock-gate, which lessens by half the time of passing. Many have been put in already - the Jack cloughs (will cost) under £1000 (for the whole canal). At this time the Leeds & Liverpool was modernising in order to compete with the railways, so it is likely that other successful canals introduced gate paddles in the middle of the nineteenth century for the same reason.
A deep lock on the Vlatava above Prague in the Czech Republic. At over 20 metres fall, such a deep lock would have been impossible without ground paddles.
What is the significance of this today? Firstly, the use and users of canals have changed radically over the last fifty years, and there are good arguments for adapting the canal environment to cope with these changes. Every year there are accidents caused by people, both inexperienced and experienced, using upper gate paddles incorrectly. Such accidents happened in the days of commercial carrying as well, when boatmen tried to work locks too quickly. The removal of upper gate paddles could certainly be suggested in terms of health and safety. Conversely, the canal system is an important historical structure, and all changes should be managed to ensure that historical integrity is not damaged. As heritage aspects of canals have been shown to be important marketing tools, the conservation of historical features is becoming more important to British Waterways. Their Waterway Character Project has been set up with the idenjpgication and conservation of the historical diversity found on our canals as an important aim.
So how does the discovery that upper gate paddles were added 70 to 100 years after canals were built affect these opposing views? Firstly, it is important to realise that the canal environment has altered over the years, and is continuing to change. This change is a vital part of the history of our canals, so when a section of canal is repaired, to what condition should it be returned - its original condition, or that of a later date? Because the canal system can be considered as a series of historical objects which are linked geographically, it could be possible to have sections of canal restored to their condition at different dates.
In relation to locks, this could mean restoring some flights with top gate paddles and others without. No doubt local canal managers know where they have particular problems with top gate paddles. Having restored different parts of a canal to its condition at different times, this could then be used as a marketing tool, adding interest to a canal holiday.
The down side would be the increased time taken to pass through locks, though this should not be too much of a problem for leisure boaters. It would also mean that gates would have to be maintained to a high standard, thereby reducing leakage, and ground paddles would need to be checked, ensuring that they are not restricted in any way. If everything was well maintained, the increased time needed to pass through locks would be minimal. Those involved with commercial carrying could be compensated through reduced licence fees or by ensuring that they are involved with the transport of maintenance materials.
Canals rely on a government grant, and on smaller canals this will only be jusjpgied by encouraging greater leisure use and increasing heritage aspects. Although commercial carrying is undoubtedly beneficial and should be supported, it must be realised that the majority of the financial aid from the government is linked to leisure. Anything which can be used to improve a canal's heritage, while at the same time making it safer, must be considered.
First published in 1999Canal page Mike Clarke
Fax: 0870 134 5609Email: