Further informationson the exhibit "Chain scale"
By lifting a pot, on one side less free chain links hang than on the other. The additional weight on one side accelerates the chain evenly. The chain can be accelerated to different degrees. The higher the stroke between the two pots - i.e. the more chain links there are on one side - the faster the chain is accelerated.
The English physicist and inventor George Atwood determined the acceleration due to gravity in 1784 with a similar falling machine.