The exact function of the cascade is related to the methods of extracting the final traces of gold from the crushed ore. There were probably washing tables between the two tanks so that a gentle stream of water could be used to wash the ore on the rough surface of the tables, the finer gold being caught in the rougher parts of the tables, and removed at the end of the process. The cascade would probably have been built towards the end of the 1st century when underground mining commenced following opencast development.