Lock (water navigation)

A lock is a device used for raising and lowering boats, ships and other watercraft between stretches of water of different levels on river and canal waterways. The distinguishing feature of a lock is a fixed chamber in which the water level can be varied; whereas in a caisson lock, a boat lift, or on a canal inclined plane, it is the chamber itself (usually then called a caisson) that rises and falls.

Locks are used to make a river more easily navigable, or to allow a canal to take a reasonably direct line across land that is not level.

Pound lock

A pound lock is a type of lock that is used almost exclusively nowadays on canals and rivers. A pound lock has a chamber (the pound) with gates at both ends that control the level of water in the pound. In contrast, an earlier design with a single gate was known as a flash lock.

Pound locks were first used in medieval China during the Song Dynasty (9601279 AD), having been pioneered by the government official and engineer Qiao Weiyue in 984. They replaced earlier double slipways that had caused trouble and are mentioned by the Chinese polymath Shen Kuo (10311095) in his book Dream Pool Essays (published in 1088), and fully described in the Chinese historical text Song Shi (compiled in 1345):

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PLAYLIST TIME:

Step IntoThis Room And Dance For Me

by: Madrugada

Closer, move in closer
Closer now than, than ever before
I doubt it that you can survive
So far from your trenches and your friends
This is where competition starts
and all of that ends
I sense a lot of tension
Loose, loose
Pull out your arsenal
Dance
(Chorus)
Step into this room and dance for me
By now we should know the music and the steps
I never asked, I never set you up
A little something for me?
A little something thrown back at me?
This is the floor, these are the rules, these are the moves
This is the room in which we dance
Close the door, say you will dance




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