Robert and Deborah Bain wrote: > The theme of the convention > is "bridges" so we would like to keep the interactives as closely > related to that as possible. Deborah, You may also want to take a look at the Nova "Super Bridges" site. Users have to select the appropriate bridge design for different kinds of spans. It also has a teacher's resource page with some simple activities that explain the physics of bridges. http://www.pbs.prg/wgbh/nova/bridge Richard Urban, Assistant Curator Historical Society of Delaware [log in to unmask]