Brought to you by a group of four Italian, Dutch, and British museums, Epact (stands for European pact) is a digital catalog of over 500 scientific and technical instruments made before 1600. Start from the handlist, a simple list of all the items in the collection, and proceed to catalog entries with pictures and two levels of text -- overview and detailed. There are also articles explaining the operation of classes of instruments, such as armillary spheres, astrolabes, the nautical hemisphere, compasses, and sundials. The search feature accommodates both experienced and novice users, since it provides a keyword box, and also instrument and maker names in drop down menus.