"I vote that we declare an emergency and land as soon as possible," I offered somewhat overly enthusiastically. Rob was already on the case, alerting center that we needed further descent. We saw on our navigation display that Jacksonville International was 75 miles to the northeast, and quickly decided that we would go there. Since I could no longer see through the windshield, we transferred control and Rob became the flying pilot. We also donned our oxygen masks and I moved my seat to its lowest and most forward position, effectively placing myself below the level of the top of the instrument panel. It was impossible to tell if the damage to the window was extensive enough to cause it to fail completely, or whether only one layer of the glass was affected. I tried not to think about what would happen if it suddenly decided to blow out at a speed of over 250 knots. Our Cracked Windshield emergency checklist provided some guidance, directing us to revert to manual pressurization and maintain a one psi differential, which I attempted to do using the controls on the overhead panel. Normally, the automatic system works great, so one doesn't get a lot of practice controlling the pressurization manually. Thus, I had a bit of a learning curve to overcome while I toggled the switches that directly move the outflow valve, and this was evident by the swifter-than-normal pressure changes felt in our ears and sinuses.