Take a look at
http://en.wikipedia.org/w/index.php?title=Wikipedia%3AReference_desk%2FScien...
It looks like Martinp23 tried to archive two day's worth of content. But some (not all) of the deleted material still shows in the revision-as-edited (i.e. in http://en.wikipedia.org/w/index.php? title=Wikipedia:Reference_desk/Science&oldid=117623727). What gives?