An egg exposed to the air is continually losing a portion of its moisture, the place of which is filled by the entrance of air, and the egg consequently becomes stale, and after a time putrid. M. Réaumur made many experiments in preserving eggs, and found that, by coating them with varnish, it was impossible to distinguish those which had been kept for a year from those newly laid; but varnish, though not expensive, is not always to be had in country places, and it also remained on the eggs placed under a hen and impeded the hatching, while in boiling them, the varnish, not being soluble in hot water, prevented them from being properly cooked. He tried other substances, and found that fat or grease, such as suet, lard, dripping, butter, and oil, were well adapted for the purpose, the best of these being a mixture of mutton and beef suet thoroughly melted together over a slow fire, and strained through a linen cloth into an earthen pan. It is only requisite, he says, to take a piece of the fat or butter about the size of a pea on the end of the finger, and rub it all over the shell, by passing and repassing the finger so that no part be left untouched; the transpiration of matter from the egg being as effectually stopped by the thinnest layer of fat or grease as by a thick coating, so that no part of the shell be left ungreased, or the tip of the finger may be dipped into oil and passed over the shell in the same manner. If it is desired that the eggs should look clean, they may be afterwards wiped with a towel, for sufficient grease or oil enters the pores of the shell to prevent all transpiration without its being necessary that any should be left to fill up the spaces between the pores. They can be boiled as usual without rubbing off the fat, as it will melt in the hot water, and when taken out of the water the little grease that is left upon the egg is easily wiped off with a napkin.
Eggs preserved in this manner can also be used for hatching, as the fat easily melts away by the heat of the hen; and by this means the eggs of foreign fowls might be carried to a distance, hatched, and naturalised in this and other countries. The French also find that a mixture of melted beeswax and olive oil is an excellent preservative.
Eggs may also be preserved for cooking by packing them in sawdust, in an earthen vessel, and covering the top with melted mutton suet or fat; as fruit is sometimes preserved. They are also said to keep well in salt, in a barrel arranged in layers of salt and eggs alternately. If the salt should become damp, it would penetrate through the pores of the shell and pickle them to a certain extent. M. Gagne says that eggs may be preserved in a mixture made of one bushel of quick-lime, two pounds of salt, and eight ounces of cream of tartar, with sufficient water to make it into a paste of a consistency to receive the eggs, which, it is said, may be kept in it fresh for two years; but eggs become tasteless when preserved with lime. It may be as well to mention here that eggs are comparatively wasted when used in making a rice pudding, as they render it too hard and dry, and the pudding without them, if properly made, will be just of the right consistency.
"Another way to preserve eggs," says Mr. Dickson, "is to have them cooked in boiling water the same day they are laid. On taking them out of the water they are marked with red ink, to record their date, and put away in a cool place, where they will keep, it is said, for several months. When they are wanted for use, they are again put into hot water to warm them. The curdy part which is usually seen in new-laid eggs is so abundant, and the taste is said to be so well preserved, that the nicest people may be made to believe that they are new laid. At the end of three or four months, however, the membrane lining the shell becomes much thickened, and the eggs lose their flavour. Eggs so preserved have the advantage of not suffering from being carried about."
"It ought not to be overlooked," says Mr. Dickson, "with respect to the preservation of eggs, that they not only spoil by the transpiration of their moisture and the putrid fermentation of their contents, in consequence of air penetrating through the pores of the shell; but also by being moved about, and jostled when carried to a distance by sea or land. Any sort of rough motion indeed ruptures the membranes which keep the white, the yolk, and the germ of the chick in their proper places, and upon these becoming mixed, putrefaction soon follows."
If the eggs are to be kept for setting, place a box, divided by partitions into divisions for the eggs of the different breeds, in a dry corner of your kitchen, but not too near to the fire; fill the divisions with bran previously well dried in an oven; place the eggs in it upright, with the larger ends uppermost, as soon as they are laid, and cover them with the bran. Mark each egg in pencil with the date when laid, and description of breed or cross. They should be kept in a cool place or a warm place according to the season. Airtight jars, closed with airtight stoppers, may be used if the eggs are intended to be kept for a very long time.
In selecting eggs for setting, choose the freshest, those of moderate size, well-shaped, and having the air-vessel distinctly visible, either in the centre of the top of the egg, or slightly to the side, when the egg is held between the eye and a lighted candle, in a darkened room. Reject very small eggs, which generally have no yolk, those that are ill-shaped, and those of equal thickness at both ends, which latter is the usual shape of eggs with double yolks. These should be avoided, as they are apt generally to prove unfertile, or produce monstrosities.
It has been stated that the sex of the embryo chicken can be ascertained by the position of the air-vessel; that if it be on the top the egg will produce a cockerel, and if on the side a pullet; but there is no proof of the truth of this, and, notwithstanding such assertions, it appears to be impossible to foretell the sex of the chick, from the shape of the egg or in any other way.
In selecting eggs for the purpose of producing fowls that are to be kept for laying only, being non-sitters, choose eggs only from those hens that are prolific layers, for prolific laying is often as characteristic of some fowls of a breed as it is of the particular breeds, and by careful selection this faculty, like others, may be further developed, or continued if already fully developed.
If carefully packed, eggs for setting may be carried great distances—hundreds and even thousands of miles—without injury; vibration and even moderate shaking, and very considerable changes of temperature, producing no ill effect upon the germ. The chief point is to prevent the escape of moisture by evaporation, and consequent admission of air. A hamper travels with less vibration than a box, and is therefore preferable, especially for a long journey. They should be packed in hay, by which they will be preserved from breakage much better than by being packed in short, close material like bran, chaff, oats, or sawdust; these being shaken into smaller space by the vibration of travelling, the eggs often strike and crack each other. The hamper or box should be large enough to admit of some soft, yielding packing material being placed all round the eggs. The bottom should be first covered with a good layer of hay, straw, or moss. It is a good plan to roll each egg separately in hay or moss, fastened with a little wool or worsted. They should be covered with well-rubbed straw, pressed down carefully and gently. The lid of the hamper should be sewed on tightly all round, or in three or four places at least. If a box is used, the lid should be fastened by cords or screws, but not with nails, as the hammering would probably destroy the germ of the egg.