 It was operated by first raising steam in the boiler; the steam was then admitted to one of the first working vessels, allowing it to blow out through a downpipe into the water that was to be raised.When the system was hot and therefore full of steam the tap between the boiler and the working vessel was shut, and if necessary the outside of the vessel was cooled.This made the steam inside it condense, creating a partial vacuum, and atmospheric pressure pushed water up the downpipe until the vessel was full.