In the second half of the eighteenth century, the Cordouan tower began to experience serious structural problems in its upper part, which had been weakened by the ravages of the sea, wind and storms. It had already been rebuilt several times, particularly the lantern, and in 1771 the Commissaire de la Marine at La Porte feared "that the top of the tower will not last very many years". Teulère himself spoke of "a future ruin". For one thing, Cordouan had become technically obsolete, not tall enough to be seen far out at sea. At the same time, a new lighting system had to be developed to replace a system in which charcoal was burnt in a large burner set in an iron lantern that had been installed in 1727. Starting in 1786, methodical preliminary studies took on a national dimension, and involved the era's leading lights, under the watchful gaze of Maréchal de Castries, the Ministry of the Navy, and under the authority of Jean-Charles de Borda, the scientific expert in maritime matters. A veritable competition began based on a set of specifications that took into account technical considerations (height and structure of the raised section) and aesthetic matters (preservation of the old part of the lighthouse). Two projects came into conflict with each other: one by Teulère and one by Claude Jean-Baptiste Jallier de Savault of the Royal Academy of Architecture. Teulère's initial project called for maintaining the older section up to the level of the chapel, with a raised section 30 pieds high that generally copied the structure and decoration of the lower part. Jallier submitted two projects that also erected an upper section 30 pieds high, topped by a new dome. In addition to the difficulties, according to Jallier, "of connecting to an older structure", the issue remained of the height of the tower, as 30 pieds was still not high enough. Initially, the outcome of the competition, which was judged by Borda, juxtaposed the projects before finally settling on the latter, drawn by Teulère in 1787, which consisted of an upper part 60 pieds tall and a conical column that was much simpler than the décor of the older tower. The new tower, which sat atop the original one, primarily met technical and utilitarian criteria. At the same time, however, it represented a successful synthesis between Louis de Foix's Renaissance tower and the Enlightenment structure of Teulère. In 1850, Chaumat-Gayet summarised the new structure well: "This most recent restoration no doubt eliminated embellishments that related to the first two storeys, but it resulted in a monument that was more regular, more solid and above all more useful for navigation."
