This is a project we just finished (incarnation #1 of a 2 column water computer). Historical references to select water computers from the past. This design was engineered to be both analog and digital. http://creative-automata.com/2014/12/18/hybrid-water-computer/ Paul Fishwick, PhD Chair, ACM SIGSIM Distinguished University Chair of Arts & Technology and Professor of Computer Science Director, Creative Automata Laboratory The University of Texas at Dallas Arts & Technology 800 West Campbell Road, AT10 Richardson, TX 75080-3021 Home: utdallas.edu/atec/fishwick Blog: creative-automata.com