File:Thompson Silvanus.jpg

Summary
Copyright has expired. The original source of the image is the 1918 edition of the Proceedings of the Royal Society A. The image was published in 1918 and so it is past the United Kingdom's "Photographs taken before 1 June 1957 expire 50 years after creation" law. See http://en.wikipedia.org/wiki/Copyright_law_of_the_United_Kingdom. See also http://en.wikipedia.org/wiki/Wikipedia:Copyrights#UK_Crown_Copyright for UK copyright information. For the US, see "In the U.S., any work published before January 1, 1923 anywhere in the world[1] is in the public domain" from http://en.wikipedia.org/wiki/Wikipedia:Public_domain, which indicates public domain status for this historical photograph.