Metal detector Bell is also credited with developing one of the early versions of a metal detector through the use of an induction balance, after the shooting of U.S. President James A. Garfield in 1881. According to some accounts, the metal detector worked flawlessly in tests but did not find Guiteau's bullet, partly because the metal bed frame on which the President was lying disturbed the instrument, resulting in static. Garfield's surgeons, led by self-appointed chief physician Doctor Willard Bliss, were skeptical of the device, and ignored Bell's requests to move the President to a bed not fitted with metal springs. Alternatively, although Bell had detected a slight sound on his first test, the bullet may have been lodged too deeply to be detected by the crude apparatus. Bell's own detailed account, presented to the American Association for the Advancement of Science in 1882, differs in several particulars from most of the many and varied versions now in circulation, by concluding that extraneous metal was not to blame for failure to locate the bullet. Perplexed by the peculiar results he had obtained during an examination of Garfield, Bell "proceeded to the Executive Mansion the next morning ... to ascertain from the surgeons whether they were perfectly sure that all metal had been removed from the neighborhood of the bed. It was then recollected that underneath the horse-hair mattress on which the President lay was another mattress composed of steel wires. Upon obtaining a duplicate, the mattress was found to consist of a sort of net of woven steel wires, with large meshes. The extent of the [area that produced a response from the detector] having been so small, as compared with the area of the bed, it seemed reasonable to conclude that the steel mattress had produced no detrimental effect." In a footnote, Bell adds, "The death of President Garfield and the subsequent post-mortem examination, however, proved that the bullet was at too great a distance from the surface to have affected our apparatus." Hydrofoils The March 1906 Scientific American article by American pioneer William E. Meacham explained the basic principle of hydrofoils and hydroplanes. Bell considered the invention of the hydroplane as a very significant achievement. Based on information gained from that article, he began to sketch concepts of what is now called a hydrofoil boat. Bell and assistant Frederick W. "Casey" Baldwin began hydrofoil experimentation in the summer