Some persons examine the eggs after the hen has sat upon them for six or seven days, and remove all that are sterile, by which plan more warmth and space are gained for those that are fertile, and the warmth is not wasted upon barren eggs. They may be easily proved by holding them near to the flame of a candle, the eye being kept shaded by one hand, when the fertile eggs will appear dark and the sterile transparent. Another plan is to place the eggs on a drum, or between the hands, in the sunshine, and observe the shadow. If this wavers, by the motion of the chick, the eggs are good; but if the shadow shows no motion, they are unfertile. If two hens have been sitting during the same time, and many unfertile eggs are found in the two nests, all the fertile eggs should be placed under one hen, and a fresh batch given to the other. The eggs should not be moved after this time, except by the hen, more especially when incubation has proceeded for some time, lest the position of the chick be interfered with, for if taken up a little time before its exit, and incautiously replaced with the large end lowermost, the chicken, from its position, will not be able to chip the shell, and must therefore perish. The forepart of the chicken is towards the biggest end of the egg, and it is so placed in the shell that the beak is always uppermost. When the egg of a choice breed has been cracked towards the end of the period of incubation, the crack may be covered with a slip of gummed paper, or the unprinted border that is round a sheet of postage stamps, and the damaged egg will probably yet produce a fine chick. It is a good plan to set two hens on the same day, for the two broods may be united under one if desirable, and on the hatching day, to prevent the newly-born chickens being crushed by the unhatched eggs, all that are hatched can be given to one hen, and the other take charge of the eggs, which are then more likely to be hatched, as, while the chickens are under the hen, she will sit higher from the eggs, and afford them less warmth when they require it most.