We present Scilog, an experimental knowledge base to facilitate scientific discovery and reasoning. Scilog extends Prolog by supporting (1) dedicated predicates for specifying and querying knowledge about scientific processes, (2) the different scales at which processes may be manifested, and (3) the domains to which values belong. Scilog is meant to invoke more specialized algorithms and to be called by high-level discovery routines. We test Scilog’s ability to support such routines with a simple search through the space of geophysical models.