The chicks are now due. I rushed to the chook house tonight to find one egg with a small hole in it, and a cheeping chicken 'stuck' inside. I carefully helped the chick get free of the shell, but when I saw blood on my hands I knew something must be wrong. I put the chick back under the hen and jumped onto the Internet. I am now more educated and have discovered that you should almost never help a chick hatch, and that the hatching process from that first hole can take 24 hours. Unfortunately the blood vessels seal over in the last few hours, and I was clearly too early with the chick.
I'm upset that I jumped in to 'help' and ended up killing our first chick. I can hear cheeping from another egg right now and will definitely be leaving these ones to their own devices.