...Examinons, maintenant que ce système est connu, l'application qu'on en avait fait à Notre-Dame de Paris. Les piles du transsept de la cathédrale ne forment point un carré, mais un quadrilatère assez irrégulier, ce qui ajoutait à la difficulté d'établir une charpente reposant sur quatre points seulement et supportant une pyramide à base octogone. La fig. 11 donne la projection horizontale de la souche de cette flèche, en supposant la section faite au-dessus du faîtage des combles...

This image comes from Dictionary of French Architecture from 11th to 16th Century (1856) by Eugène Viollet-le-Duc (1814-1879).

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