Candling Eggs

One of my early childhood memories... I am sitting on my Uncle Cecil's lap in the henhouse, candling eggs.
Before setting eggs under the hen to brood, we would candle the eggs to make certain they were fresh.
We would hold the eggs up to a lamp in the dark henhouse with the large end up.
Good eggs look clear and the white spot, or air cell, at the end of the egg is small, not larger than a dime. The yolk is at the center.
If the egg cell is large, and a dark yolk moves around, the egg is not fresh.
While the eggs are brooding, they can also be candled to check the progress of the embryos. The video above shows a live embryo moving around in an egg that is being candled