... 1999Scientific American Presents (ISSN 104 8-0 943), Volume 10,Number 4,Winter 1999,publishedquarterly by Scientific American, Inc.,415 Madison Avenue,New York,NY 1001 7-1 111. Copyright© 1999 by Scientific American, ... ENGINEERING 19Copyright 1999 Scientific American, Inc.20 SCIENTIFIC AMERICAN PRESENTSPerhaps no dam in history hasbeen studied to the extent ofthe multibillion-dollar struc-ture currently rising ... cur-rent. Once again, though, the probe re-sponds to this change, coming closer tothe surface to preserve a constant current26 SCIENTIFIC AMERICAN PRESENTSTHE BIG AND THE SMALLMIX-AND-MATCH...