In these days the historian sets himself with devotion to follow in all its involutions the long chain of thought and effort by which man has been led from his primitive barbarism to the well-being of modern civilization, and to his domination--every day more complete and more intelligent--over the minor forces of nature. It is the duty of criticism, as its methods gradually perfect themselves, to add daily to its perspicacity and powers of observation, and to lessen as much as possible the occasions, still so numerous, when the thread of evidence breaks in its hands and the true relations of facts to each other become obscured. Even yet we cannot say for certain to which nation of the ancient world the invention of the arch belongs. In those remote ages the principle may have been discovered more than once or twice in different and distant countries whose inhabitants were busied over the same task. We have no reason to believe that Chaldaea learnt the secret from Egypt, or Etruria from the East. It is none the less true, however, that the unknown architects of Babylon and Nineveh made full use of it at an earlier date and in more intelligent fashion than any of their rivals. To them must be given the credit of being the masters and art-ancestors of the men who built the Pantheon and the Church of Saint Sophia, Santa Maria del Fiore, and Saint Peter's in Rome, and more especially of those great modern engineers to whom the principle of the arch has been a chief element in their success. NOTES: [280] _Art in Ancient Egypt_, vol. ii. p. 82. [281] This chamber is 7 feet long, 3 feet 7 inches wide, and 5 feet high. TAYLOR, _Journal of the Royal Asiatic Society_, vol. xv. p. 272. [282] STRABO, xvi. 1, 5. DIODORUS, ii. 10. [283] PLACE, _Ninive_, vol. i. pp. 170-182 and 256-259, vol. iii. plates 9-18. [284] PLACE, _Ninive_, vol. iii. plate 2. [285] PLACE, _Ninive_, vol. i. p. 128. [286] LAYARD, _Nineveh_, vol. i. p. 134; vol. ii. pp. 79 and 261. _Discoveries_, pp. 162-165. [287] PLACE, _Ninive_, vol. i. pp. 269-280 and plates 38 and 39. [288] We have endeavoured to combine M. Thomas's longitudinal elevation, vertical section, and transverse section (PLACE, _Ninive_, plate 38), in our single cut. [289] The same process was employed at Nimroud in a drain or water channel, of which LAYARD gives a sketch (_Discoveries_, p. 164). In connection with these vaults we must remember that a pointed arch has no key properly speaking; the top stone is merely a joint. It looks as if the Assyrian architect had a kind of instinctive appreciation of the fact. [290] The slope, the height, and the width of this channel are not the same throughout. In some places it is wide enough to allow two men to walk abreast in it. [291] LAYARD, _Nineveh_, vol. i. p. 79. [292] OTTFRIED MUeLLER, _Handbuch der Archaeologie der Kunst_, Sec. 107 and 168 (3rd edition). [293] _Art in Ancient Egypt_, vol. i. p. 112, and vol. ii. chap. ii. Sec. 4.