Why 2 gates at the bottom??

[fender]

I often wonder about waterways like the Fossdyke. How did boats get onto it?

 

The Romans had built water gates so a pound lock wouldnt have been concievably difficult. Or did they just use a water gate and permitted access when the Trent and Fossdyke made a level?

[Pluto]

I often wonder about waterways like the Fossdyke. How did boats get onto it?

 

The Romans had built water gates so a pound lock wouldnt have been concievably difficult. Or did they just use a water gate and permitted access when the Trent and Fossdyke made a level?

I suspect some form of water gate. Chamber locks developed where there was insufficient water for flash locks, and their introduction would also mirror an increasing need for uninterrupted passage by boats. On an early canal where the tideway ensured water levels, there would be little point in boats leaving the canal at other than high water.

[Guest]

Thinking outside the box...

 

Maybe it is not a modern phenomenon that workers try to use shortcuts to speed up their job. As I understand it, gates should be closed after you leave the lock? Perhaps siting the lock on the non tow path side forced the boater/lockwheelers to close the gate, lest he be stuck on the non towpath side?

 

 

and that possibly explains why the swing bridges on the L&L swing from the non tow-path side too.

 

 

 

Thanks for all the replies folks, it's clearly a more complex issue than I first realised.

[Rick-n-Jo]

Thinking outside the box...

 

Maybe it is not a modern phenomenon that workers try to use shortcuts to speed up their job. As I understand it, gates should be closed after you leave the lock? Perhaps siting the lock on the non tow path side forced the boater/lockwheelers to close the gate, lest he be stuck on the non towpath side?

 

 

and that possibly explains why the swing bridges on the L&L swing from the non tow-path side too.

 

 

 

Thanks for all the replies folks, it's clearly a more complex issue than I first realised.

 

When the canals were worked, exit gates were mainly left open, and arguably still should be!

 

A boatman would not have been "Stuck on the wrong side" or walked around in modern wussy style, they quickly evolved tecniques needing least effort, including stepping across the gap, no doubt, but also operating the far gate with a shaft or boathook.

 

Swing bridges etc are on the non towpath side so that they do not obstruct the towline.

[Guest]

Swing bridges etc are on the non towpath side so that they do not obstruct the towline.

 

Ahh......... logical when you think about it....

[fender]

I read in one book that the earliest pound locks were used where differences in water levels were expected. EG where there are tidal differences, and this is attributed to the Dutch about 1373 at Vreeswijk, so possibly just a water gate was used at Torskey. The book tells us that pound locks were very possibly invented in Mesopotamia about 2000BC (but it all depends on how one interprets a passage in the Gilgamesh.)

 

China didnt need to invent pound locks as the very gentle rises in the waterways meant their flash locks that had been in use for around a thousand years before their first pound lock arrived were sufficient. The first pound lock in China was about 980ad, these actually were not successful because the flash locks were still much preferred - the introduction of pound locks meant tolls were imposed or massively increased and offered no better transit times. This explains why many renaissance travellers to China have been disappointed not being able to find a pound lock there.

 

PS there's an answer to Magpie Patrick's previous post that single gates didnt preceede mitre gates.

Edited February 13, 2010 by fender

[Tiny]

On the BCN I was taught that Brindley built two bottom one top gate locks due to weight contraints but Smeaton, who came in after Brindley died, prefered one top, one bottom. (Hence the odd extra lock (number 20?) in the Wolverhampton flight - this added by Smeaton. His was also the Birmingham and Fazeley canal which used to have some lovely paddle gear on the bottom end gate too until BW did away with it on all but one lock.

 

After Smeaton only canals built on the cheap (like the South Stratford) had single top and bottom gates while others prefered three and even 4 gates per narrow lock. But, unlike a lot of Brindley locks - which offered a walkway across the lock below the bottom gates to make passage across quick and safe for the boatees, a lot of the later locks, like those on the Llangollen and the Shroppie, had no bottom end bridge (though one was possible - maybe raised a bit to give clearence below) as by then canal builders worked more from offices than close to the cut where they might see advantages.

 

Given BWs love of safety I always think its a shame that they don't install some of these safety bridges now on the Staffs & Worcester north, Llangollen and Shroppie- it would save the wife miles of walking round!

[Pluto]

China didnt need to invent pound locks as the very gentle rises in the waterways meant their flash locks that had been in use for around a thousand years before their first pound lock arrived were sufficient. The first pound lock in China was about 980ad, these actually were not successful because the flash locks were still much preferred - the introduction of pound locks meant tolls were imposed or massively increased and offered no better transit times. This explains why many renaissance travellers to China have been disappointed not being able to find a pound lock there.

There may have been pound locks on early Chinese canals, though by the time the country was visited by Europeans, in the 18th century, these had been removed and replaced by inclines and flash locks. The earliest canal in China was the Lingqu or Magic canal, first constructed circa 240 BC. The canal links the head waters of two rivers in quite mountainous country. It is still there and can be seen at 国宝档案20081216 -- 揭秘灵渠(下)

http://www.youtube.com/watch?v=qQIDGW-MWEE...feature=related

 

The 1200 mile long Grand Canal came later, being constructed from 600AD. Its route has changed considerably over the years, not least because of the silting and movement of the Yellow River which carries around 10% by volume of silt. Its estuary has moved quite suddenly some 400 miles north or south on several occasions, causing problems for those maintaining the Grand Canal. The development of canal technology in China has still to be researched fully. There are copies of scrolls illustrating the canal in the 18th century at http://www.learn.columbia.edu/nanxuntu/htm...oll_index.html# By that time flash locks and inclines were the norm, though not necessarily as we know them in the west.

 

A theory has been suggested by some historians that the idea for the pound lock was brought to Italy by the Chinese, who sent a fleet of boats westward on a voyage of discovery around 1428.

[fender]

There may have been pound locks on early Chinese canals, though by the time the country was visited by Europeans, in the 18th century, these had been removed and replaced by inclines and flash locks. The earliest canal in China was the Lingqu or Magic canal, first constructed circa 240 BC. The canal links the head waters of two rivers in quite mountainous country. It is still there and can be seen at 国宝档案20081216 -- 揭秘灵渠(下)

http://www.youtube.com/watch?v=qQIDGW-MWEE...feature=related

 

The 1200 mile long Grand Canal came later, being constructed from 600AD. Its route has changed considerably over the years, not least because of the silting and movement of the Yellow River which carries around 10% by volume of silt. Its estuary has moved quite suddenly some 400 miles north or south on several occasions, causing problems for those maintaining the Grand Canal. The development of canal technology in China has still to be researched fully. There are copies of scrolls illustrating the canal in the 18th century at http://www.learn.columbia.edu/nanxuntu/htm...oll_index.html# By that time flash locks and inclines were the norm, though not necessarily as we know them in the west.

 

A theory has been suggested by some historians that the idea for the pound lock was brought to Italy by the Chinese, who sent a fleet of boats westward on a voyage of discovery around 1428.

 

Chinese researchers themselves actually refute the western theories that they had pound locks earlier than 980ad, which is what I was trying to say in my previous post. Yes I read that inclined planes replaced some of the pound locks as well, but the chinese's sequence of originally using flash locks, then replaced by pound lock, and replaced by flash locks again was what intrugued me the most.

 

PS> The Ling Chhu Canal had what were termed entry and exit gates over a lengthy section but these did not constitute what anyone would call a pound lock. The first pound lock on the Ling Chhu was built in 1060.

Edited February 14, 2010 by fender

[Pluto]

Chinese researchers themselves actually refute the western theories that they had pound locks earlier than 980ad, which is what I was trying to say in my previous post. Yes I read that inclined planes replaced some of the pound locks as well, but the chinese's sequence of originally using flash locks, then replaced by pound lock, and replaced by flash locks again was what intrugued me the most.

 

PS> The Ling Chhu Canal had what were termed entry and exit gates over a lengthy section but these did not constitute what anyone would call a pound lock. The first pound lock on the Ling Chhu was built in 1060.

I think one problem with discussing Chinese canals is that some engineering structures, although having similar names to those in the west, actually perform slightly different functions. Many Chinese canals were/are used for land drainage and irrigation as well as navigation, so their solutions to change in level are somewhat different to those used in Europe, where many canals were primarily for transport. The Grand Canal was also only used for shortish periods each year, though quite intensively then, for the movement of rice from the Yangtze basin to Beijing and for the returning empty boats. This traffic also had to fit in with the varying flows of the Yellow River, and the so-called locks at the river junction were designed to keep the vast amounts of silt being carried down the river from entering the canal system. More conventional flash locks and inclines were used elsewhere. As you mention, the type of structure for coping with changes in water level varied over time. The chinese are putting together a World Heritage application for the Grand Canal, and I hope that more information about the history of Chinese canals will be published as part of the application.