My White Silkie hen, Amelia, went broody about a month ago. I am not sure exactly when, as my younger brother collects the eggs and I am more caught up with taking care of the goats now. But the day after I discovered that she was broody, we had eggs for dinner and there were at least 7 eggs with developing chicks inside (I'm guessing they were 10-14 days along). All the chicks were dead of course, as they had been in the fridge for more than a day. 
On September 19 I gave Amelia about 14 more eggs. In the past she's not been a very good broody hen, only hatching 1 chick out of say, 10 eggs. A year or two ago (her last hatch before this one) she hatched two chicks and disowned one of them, I guess because she was only used to raising 1 chick? But that was okay with me because one of our other hens was broody at the same time and joyfully excepted the poor little rejected chick.
But anyway, yesterday I candled Amelia's large brood of eggs. One egg she had broken open a few days previous to this (it was rotten), so I candled the remaining 13. If I remember correctly, 9 eggs had what appeared to be live chicks in them (2 were clearly moving inside!) - they all had visible veins and looked to be the right size. One egg was obviously rotten, it stunk so badly and we so threw it out. The other 3 I couldn't really tell whether or not they had live chicks inside.
But one of the eggs in which a chick was moving had been cracked the day after Amelia had started setting on it (the 20th). A few hours after candling it I checked on Amelia and the egg was even more cracked then before.
So I took it out and set up our old(ish) incubator that hadn't been used in years, and turned it on and put the egg in it. That was yesterday afternoon. The egg seems to be fine so far, I hope the chick is still alive and will make it...
Should I put some more of Amelia's eggs in the incubator to ensure their safety? We don't have very good broody hen accommodations, and so sometimes other chickens will go into the nest and lay an egg in it (which I take out). I think that was how egg #12 got cracked.

On September 19 I gave Amelia about 14 more eggs. In the past she's not been a very good broody hen, only hatching 1 chick out of say, 10 eggs. A year or two ago (her last hatch before this one) she hatched two chicks and disowned one of them, I guess because she was only used to raising 1 chick? But that was okay with me because one of our other hens was broody at the same time and joyfully excepted the poor little rejected chick.
But anyway, yesterday I candled Amelia's large brood of eggs. One egg she had broken open a few days previous to this (it was rotten), so I candled the remaining 13. If I remember correctly, 9 eggs had what appeared to be live chicks in them (2 were clearly moving inside!) - they all had visible veins and looked to be the right size. One egg was obviously rotten, it stunk so badly and we so threw it out. The other 3 I couldn't really tell whether or not they had live chicks inside.
But one of the eggs in which a chick was moving had been cracked the day after Amelia had started setting on it (the 20th). A few hours after candling it I checked on Amelia and the egg was even more cracked then before.

Should I put some more of Amelia's eggs in the incubator to ensure their safety? We don't have very good broody hen accommodations, and so sometimes other chickens will go into the nest and lay an egg in it (which I take out). I think that was how egg #12 got cracked.