a cheap way to do it is get an old shoe box, cut a couple of different sized round holes in it, they should be about a quater of the size of the egg at it's roundest point. Making several different sizes will allow you to compare which candles each egg and each size better. Get a good torch (o flashlight as they're calling in America), put the shoe box over the top while placing the egg to sit in the holes. Candle from each side, and gentle turn it. If there's a chick forming it will appear as ether a dark patch, or if it's nearly fully developed, nothing but the air sack will be visible. If it's not fertile or not under a chook, you may see a yolk if the egg's white or thin shelled enough. If you didn't find a hen sitting on them, they're probably not growing a baby, but it's always fun to have a look inside to see what's going on.
