The envelope which contains the foetus of various animals, and which, being voided by the parent, is subsequently matured by. incubation. This may also be effected by means of prolonged artificial heat; and in Egypt the art of hatching chickens by means of ovens has long been practised, but it is there only known to the inhabitants of a single village, named Berme, and to those that live at a small distance from it. Towards the beginning of autumn they scatter themselves all over the country, where each person among them is ready to undertake the management of an oven, each of which is of a different size, but in general they are capable of containing from forty to fourscore thousand eggs. The number of these ovens placed up and down the country is about 386, and they usually keep them working for about six months; as, therefore, each brood takes up in an oven, as under a hen, only twenty-one days, it is easy in every one of them to hatch eight different broods of chickens. Every Bermean is under the obligation of delivering to the person who entrusts him with an oven, only two-thirds of as many chickens as there have been eggs put under his care; and he is a gainer by this bargain, as more than two-thirds of the eggs usually produce chickens.
In order to make a calculation of the number of chickens yearly so hatched in Egypt, it has been supposed that only two-thirds of the eggs are hatched, and that each brood consists of at least 30,000 chickens; and thus it would appear that the ovens of Egypt give life yearly to at least 92,640,000 of these animals. As it is of great importance in a zoological, and, to a certain extent, even in an economical point of view, to be able to transport eggs fresh from one country to another, it has been proposed, as the best method of effecting this, to varnish them with gum arabic, and then imbed them in pounded charcoal, which being a non-conductor of heat, a uniform temperature will be preserved.