Should Lee move north, leaving a force "tempting you to fall upon it... In one word, I would not take any risk of being entangled upon the river, like an ox jumped half over a fence, and liable to be torn by dogs, front and rear, without a chance to gore one way or kick the other...."
This is from Stephen Sears
Gettysburg which is quite a good book about this battle and the events leading up and following it.
http://www.barnesandnoble.com/w/gett...=9780618485383