Our figure has been compiled from the plans and elevations of Prisse with a view to making the arrangement easily understood (Fig. 50); it represents the lower part of one of the walls in question. According to M. Viollet-le-Duc, the Egyptian architects had recourse to this contrivance in order to guard against the effects of earthquakes. He shows clearly that a wall built in such a fashion would offer a much more solid resistance to their attacks than one with foundations composed of horizontal courses.[85] [85] VIOLLET-LE-DUC, _Histoire de l'Habitation humaine_, pp. 85-88. Alberti and other Renaissance architects recommended this method of construction for building upon a soft surface. (_L'Architettura di Leon Batista Alberti, tradotta in lingua fiorentina da Cosimo Bartoli_, Venice, 1565, 4to, p. 70.) If we are to take it as established that the vault or arch was among the primitive methods of Egyptian construction, we have no reason to believe that _off-set_ arches were older, in Egypt at least, than true arches. We have described this form of arch elsewhere, and explained the contrivance by which the superficial appearance of a vault was obtained.[86] The process could obviously only be carried out in stone. We shall here content ourselves with giving two examples of its employment. [86] See p. 110, Vol. I., and Figs. 74, 75, 76. [Illustration: FIG. 49.--Elliptical vault; Thebes.] [Illustration: FIG. 50.--Foundations with inverted segmental arches; compiled from Prisse.] The first dates from the eighteenth dynasty, and occurs in the temple of Dayr-el-Bahari.[87] Our Fig. 51 gives a transverse section of a passage leading to one of the chambers cut in the rock. Fig. 52 offers a view in perspective of the same passage and of the discharging chamber which really bears the thrust of the weight above. [87] See p. 111, Vol. I., _et seq._ [Illustration: FIG. 51.--Transverse section of a corridor at Dayr-el-Bahari; from Lepsius, i. pl. 87.] [Illustration: FIG. 52.--Section in perspective through the same corridor; composed from the elevation of Lepsius.] The second example of this construction comes from a famous work of the nineteenth dynasty, the temple of Seti I. at Abydos. Our figure (53) shows one of the curious row of chapels in which the originality of that building consists.[88] This quasi-vault, for which Mariette finds a reason in the funerary character of the building, has been obtained by cutting into three huge sandstone slabs in each horizontal course. The stone forming the crown of the vault is especially large. [88] See also pp. 385-392, Vol. I. and Fig. 224.--Our perspective has been compiled from the _Description de l'Égypte_, from Mariette's work and from photographs. [Illustration: FIG. 53.--Vaulted chapel at Abydos.]