Get a whole year of CuriosityStream for just $12 by going to https://curiositystream.com/stevemould and using the promo code stevemould at checkout. Heron's Fountain is a mind bending hydrodynamic mechanism. It appears to be perpetual motion but it fact it's a really clever mix of pneumatics and hydraulics. This 2D presentation helps to explain how it works. Image credits: Soxhlet extractor image - Vivi! (https://commons.wikimedia.org/wiki/File:Soxhlet.JPG) Washout toilet - Flammingo (https://commons.wikimedia.org/wiki/File:Klo_flachsp%C3%BCler_mit_altem_Sp%C3%BClkasten.JPG) Toilet diagrams - SouthHamsian (https://en.wikipedia.org/wiki/File:Four_types_of_pedestal_WC.svg) You can buy my books here: https://stevemould.com/books You can support me on Patreon here: https://www.patreon.com/stevemould just like these amazing people: Matthew Cocke Glenn Watson Joseph Rocca Joël van der Loo Doug Peterson Rashid Al M Paul Warelis Will Ackerly Heather Liu Twitter: http://twitter.com/moulds Instagram: https://www.instagram.com/stevemouldscience/ Facebook: https://www.facebook.com/stevemouldscience/ Buy nerdy maths things: http://mathsgear.co.uk/