The Egyptians regarded man as composed of various different entities, each having its separate life and functions. First, there was the body; then the _Ka_ or double, which was a less solid duplicate of the corporeal form--a coloured but ethereal projection of the individual, reproducing him feature for feature. The double of a child was as a child; the double of a woman was as a woman; the double of a man was as a man. After the double (_Ka_) came the Soul (_Bi_ or _Ba_), which was popularly represented as a human- headed bird; after the Soul came the "_Khû_," or "the Luminous," a spark from the divine fire. None of these elements were in their own natures imperishable. Left to themselves, they would hasten to dissolution, and the man would thus die a second time; that is to say, he would be annihilated. The piety of the survivors found means, however, to avert this catastrophe. By the process of embalmment, they could for ages suspend the decomposition of the body; while by means of prayer and offerings, they saved the Double, the Soul, and the "Luminous" from the second death, and secured to them all that was necessary for the prolongation of their existence. The Double never left the place where the mummy reposed: but the Soul and the "_Khû_" went forth to follow the gods. They, however, kept perpetually returning, like travellers who come home after an absence. The tomb was therefore a dwelling-house, the "Eternal House" of the dead, compared with which the houses of the living were but wayside inns; and these Eternal Houses were built after a plan which exactly corresponded to the Egyptian idea of the after-life. The Eternal House must always include the private rooms of the Soul, which were closed on the day of burial, and which no living being could enter without being guilty of sacrilege. It must also contain the reception rooms of the Double, where priests and friends brought their wishes or their offerings; the two being connected by a passage of more or less length. The arrangement of these three parts[26] varied according to the period, the place, the nature of the ground, and the caprice of each person. The rooms accessible to the living were frequently built above ground, and formed a separate edifice. Sometimes they were excavated in the mountain side, as well as the tomb itself. Sometimes, again, the vault where the mummy lay hidden, and the passages leading to that vault, were in one place, while the place of prayer and offering stood far off in the plain. But whatever variety there may be found as to detail and arrangement, the principle is always the same. The tomb is a dwelling, and it is constructed in such wise as may best promote the well-being, and ensure the preservation, of the dead.