avant la lettre, Fig. 4a.
Fig. 4a. [cropped to square]
Wheeler P. Davey (1886-1959 *). “Radiography of Metals.” Transactions of the American Institute of Mining Engineers 53 (1916) : 150-160
University of California copy, digitized October 31, 2012
...by well-known means... *
avant la lettre; grays; radiography; sciagraphy; skiagraphy
W. P. Davey