Drake's Plate of Brass - Forty Years Later, Science Sheds New Light

Forty Years Later, Science Sheds New Light

In the early 1970s, physics caught up to Haselden's original findings. Professor James D. Hart, director of the Bancroft Library, assembled a re-testing plan in preparation for the 400th anniversary of Drake's landing. Hart reached out to Research Laboratory for Archaeology, the History of Art at Oxford University, and the Lawrence Berkeley Laboratory for a detailed analysis. The tests included x-ray diffraction, stereo microscopy, and additional metallurgical analysis. X-ray diffraction and gamma-ray absorption tests revealed the plate to be too smooth, made by modern rolling equipment, not hammered flat by a sixteenth century hammer. Dr. Frank Asaro at the Lawrence Berkeley Laboratory of the University of California, Berkeley, working with colleague Helen Michels, used neutron activation analysis to study the plate and found that it contained far too much zinc and too few impurities to be Elizabethan English brass, while containing trace metals that corresponded to modern American brass. Prof. Cyril Stanley Smith of MIT examined the plate under a stereo microscope and found the edges to be consistent with modern cutting equipment.

No paint visible under ultraviolet light has been detected on the back of the plaque.