Thinnking better of it, Lincoln did not send the letter. See: http://www.npr.org/templates/story/story.php?storyId=100531323
(Image of the first page of the letter.)
" The first page of a letter Lincoln wrote to Gen. George Meade expressing disappointment that he didn't go on and attack Gen. Robert E. Lee at the Potomac River after Gettysburg. But the letter was so condemning that he did not send it — it has a note that says, "never sent or signed." From 'In Lincoln's Hand'/Bantam Books. Courtesy of The Library of Congress "
It would seem Meade had really upset lincoln in his telegraphic correspondennce, but lincoln's perhaps better and wiser nature stayed his respons. Harry Truman did the same upon occaision. Stan