The precise location of the cornerstone was lost during the two centuries following the ceremony due to attack and multiple expansions of the original building. In 1993, Architect of the Capitol George White, following a protracted search involving the use of ground-penetrating radar, electromagnetic induction and induced polarization, announced he had found a large stone buried beneath one section of the foundation that was "obviously a ceremonial stone," and declared it was probably the cornerstone of the building. No sign of the original silver plaque was discovered, and experts believe it may have been dislodged and destroyed during the 1850 construction of the Senate chambers.