Crack the CIA code

I've been trying to crack the code outside the CIA headquarters for some time. Anyone have any ideas?

http://www.cia.gov/cia/information/tour/krypt.html
http://www.cia.gov/cia/information/tour/kryptos_code.html

These are the portions already solved:

Between subtle shading and the absence of light lies tthe nuance of iqlusion It was totally invisible hows that possible? They used the earths magnetic field x the information was gathered and transmitted undergruund to an unknown location x does langley know about this? They should its buried out there somewhere x who knows the exact location? Only WW this was his last message x thirty eight degrees fifty seven minutes six point five seconds north seventy seven degrees eight minutes fourty four seconds west id by row s slowly desparately slowly the remains of passage debris that encumbered the lower part of the doorway was removed with trembling hands I made a tiny breach in the upper left hand corner then widening the hole a little I inserted the candle and peered in the hot air escaping from the chamber caused the flame to flicker but presently details of the room with emerged from the mist X can you see anything?

The last 97 characters use something different. That is what must be solved.