[122] Merzario, I Maestri Comacini, Vol. I. chap. ii. pp. 87-89.
[123] See Article on the Round Towers in St. Peter's Magazine for May 1898.
[124] Pisa illustrata nelle Arti del Disegno.
[125] Professor Ridolfi, L' Arte in Lucca, p. 74, et seq.
[126] Sull' Architettura e sulla Scultura in Venezia nel medio evo sino ai nostri giorni. Studi di P. Selvatico, cap. ii. p. 48.
[127] Selvatico, Storia della Scultura, Lib. II. cap. ii.
[128] Storia di Como, vol. i. p. 537.
[129] In a work by Luigi Mazara (Temple antédiluvien découvert dans l'île de Calypso, Paris 1872) there are two engravings of gateways, one a subterranean one at Alatri in Latium, which is said to have been the work of Saturn, and is called the Porta Sanguinaria; the other of Cyclopean architecture was also in Latium, and called Porta Acuminata; both of them are pointed arches. This would carry the invention back to 2000 B.C. Many of the subterranean aqueducts of Rome have acute arches for purposes of strength.
[130] Seroux, Histoire de l'art par les monuments, p. ii. Paris.
[131] Hope, Storia dell' Architettura, cap. xxxiii.