Left image — original to the blog theme.
Middle image — “High Bridge in Loop” [Union Pacific Railway, near George Town Colorado]. W.H. J [Jackson] & Co. Made available by The Bancroft Library, University of California, Berkeley. Found at: http://content.cdlib.org/ark:/13030/tf596nb5hg/
Right image — “Generation Gap” by Joi Ito. (CC BY 2.0). Taken: April 11, 2007. Found at: http://flickr.com/photos/joi/455111587/