In 1843 Cauchy acted as the sponsor of Barre de Saint-Vennat(1797-1886). Saint-Venant, who at the age of forty-six had a considerable record of important publications, received no more than six votes out of a total of fifty-four.
Another fifteen years were to elapse before there was another vacancy in the mechanics section. The section again placed Saint-Venant in equal first place but he received no more than twelve votes from the Academy, compared with forty-three for his rival Clapeyron. Cauchy had died the previous year but alliances were not easily forgotten. When there was a further vacancy in 1864, the mechanics section overlooked completely the candidature of Saint-Venant, who had to write in as if he were some junior unknown mathematician. Only in 1868 did the Academy agree to admit Saint-Venant, who had by then reached the age of seventy-one!

In the few years of power granted to him as an Academician, Saint-Venant ated as the patron of another Catholic mathematician of the first rank, Boussinesq (1842-1929) was to make important contributions to nearly all branches of mathematical physics and notably to hydrodynamics. He did not have the advantage of belonging to any of the grandes écoles. He was largely self-taught, owing much of his early education to his uncle, a priest. His thesis of 1867 on the diffusion of heat won him the favourable attention of Saint-Venant, who henceforth acted as his patron. In 1870 Saint-Venant, acting as rapporteur for a memoir by Boussinesq, praised the author for his “remarkable spirit of invention, constantly supported by greated analytical ability”. Boussinesq made repeated, but unsuccessful, attempts to enter the Academy in 1868, 1871, 1972(twice), 1873, 1880 and 1883. By this time Saint-Venant had become the doyen of the mechanis section and thus the person with responsibility for comparing the merits of rival candidates. His report for the election of 1886 has survived. It shows an impassioned advocancy of his protégé who, he pointed out, was unique in being the only survivor of these early elections not to have been elected to the Academy. He must have previtely compared the fate of his protégé with his own situation earlier. Saint-Venant’s advocacy was one of his last acts. He died on 6 January 1886 without knowing Boussinesq would succeed. When the vote was taken on 18 January 1886 Boussinesq was elected by a narrow majority, receiving twenty-nine votes compared with twenty-six given to his rival, the engineer Deprez.
Although Boussinesq lived a simple existence devoted to mathematics, he was also passionately interested in the relevance of science to religion. In conversation he would go out of his way to raise difficult theological problems and he even extracted philosophical conclusions from his mathematics. In his study of solutions to differential equations he drew attention to the possibility of indeterminism, which he suggested applied uniquely to living systems. Taking this further, he argued in favour of human free well. It was in a spirit of Christian humility that he spoke of “the smallness of the ensemble of our unclouded knowledge lost in an ocean of darkness”.

Maurice Crosland Science under Control:the French Academy of Sciences 1795-1914. Cambridge University Press, 1992, p225-226