We now come to the physicists. To begin with the most prominent representatives of the science of optics, which was developed especially during the first half of the century, there are to be named chiefly _Fresnel_, _Frauenhofer_, _Fizeau_, _Foucault_. _A. Fresnel_ (died 1827), the originator of the modern theory of light, clung to his conviction of the spirituality and immortality of the soul. _Frauenhofer_ (died 1826) showed himself to be a man of refinement and of kindness, which only occasionally was disturbed by natural irritability: he was much devoted to his religion, so that even his guests while at his house had to observe the abstinence prescribed by the Church; this was quite significant, considering the indifference of his times in this respect. _Fizeau_ (died 1896), too, was a staunch Catholic, who fearlessly testified to his belief, even before the Paris Academy. Though his work was of the first rank, France’s chief marks of honour passed him by, and little notice was even given to his death. A significant fact. “These circumstances,” so writes _Kneller_, “induced us to inquire for particulars; and through the services of friends we obtained information in Paris from most reliable source that _Fizeau_ was a faithful Christian, who fulfilled his religious duties. For this very reason his name had been stricken, at the Centenary of the Academy, from the list of candidates for the cross of the legion of honor, notwithstanding the fact that, on the strength of his scientific achievement, he should long have been Commander and even Grand Officer of this order.” _Cornu_ was the only one to protest against this slight. _Foucault_ (died 1868) had, in the time of his restless scientific work, taken an unsympathetic attitude towards the Catholic religion. In his last illness he returned, step by step, to his Creator and Redeemer, in whom he found his comfort, and he breathed his last in peace with God and the Church.