You mean the DEADLINE at Rock Island, Johnson's Island, Camp Douglas, etc., called their invention by a different name? What was it? The Line of Eternal Sleep?
Nice photo, but other than the caption-writer's opinion, there is not much by way of substantiation.
For an interesting contrast of POW camps, see this picture of the hovels at Andersonville:
http://lcweb2.loc.gov/cgi-bin/query/r?pp/ils:@field(NUMBER+@band(cph+3c22695))