Mont Blanc massif led to calls to limit access to the most popular summits and for the mountains to be treated with greater respect. The Mont Blanc massif has provided numerous opportunities for academic research, dating back to the very first ascent of Mont Blanc in 1786 during which Michel Paccard carried scientific equipment to confirm it as the highest summit. In 1820, an ill-fated expedition led by Dr Hamel included pigeons intended for release at varying altitudes to measure the impact of reduced air density on their ability to fly. In 1890, Joseph Vallot built a small meteorological observatory at approximately between
Jacques Gabriel of de Cotte's retirement in December 1734 and held the post until he was succeeded by his "vastly more gifted" son, Ange-Jacques Gabriel in 1742. Gabriel's work in Paris has been much remodelled. Mariette's "Architecture françoise" offers plates illustrating several "hôtels particuliers" by Gabriel. He completed the Palais Bourbon (begun by Giardini, continued by Pierre Cailleteau Lassurance). He completed the Hôtel de Lassay nearby. He was responsible for the Hôtel Peyrenc de Moras (de Biron), 1728-31. "Il étoit expert dans la conduite du bâtiment, mais il n'auroit pas pu dessiner le moindre bout d'ornement"; ). Jacques Gabriel Jacques Gabriel (1667–1742)