Most of his book consists of brief records of men who maintained their activity to a great age. Many of these are familiar enough but we sample a few. Mommsen, for example, frail and small, lost his library by fire when he was sixty, a calamity that all thought would end his career. But he did much of his best work later, toiling on his _History of Rome_ nearly to his death in his eighty-sixth year. George Ives, when his friends congratulated him on attaining his hundredth year, was found at work in the field and said that even if he knew he were to die the next day he should “carry on” as if he were immortal. Mrs. H. W. Truex on her 96th birthday in 1904 finished a quilt of nine hundred and seventy-five pieces and during the previous year had completed six such. Sir Joseph Hooker, the botanist, worked almost up to his death at 87, holding that rich natures develop slowly. Carlyle published the last volume of his _Frederick the Great_ at the age of 69; Darwin, his _Descent of Man_ at 62; Longfellow wrote his _Morituri Salutamus_ for the fiftieth anniversary of his graduation; W. C. Bryant published his translation of the _Odyssey_ at the age of 76; O. W. Holmes wrote his “Guardian Angel” at 70 and “Antipathy” at 76, while the “Iron Gate” was for a breakfast given in honor of his seventieth birthday; George Bancroft at 82 published his _History of the Foundations of the Constitution of the United States_; Frances Trollope, failing in business at the age of nearly 50 and a stranger in this country, turned to a literary career, and between the ages of 52 and 83 wrote upwards of a hundred volumes, mostly novels of society; Humboldt, at the age of 74, began his _Cosmos_, the fourth and last volume of which was issued the year before his death, in 1858, at the age of ninety; Cervantes published the last part of his _Don Quixote_ at 78; Goethe wrote till he was 80 and finished the second part of _Faust_ only shortly before his death; Victor Hugo wrote his _Annals of a Terrible Year_ at 70, and his _Ninety-Three_, which some regard as his best story, at the age of 72; Mary Sommerville kept up her scientific activities and at 92 said she could still read books on the higher algebra four to five hours in the forenoon; Weir Mitchell wrote his _Hugh Wynne_ at 66 and _Constance Trescot_, a very remarkable psychological study of a woman, when he was 76. A deposed minister began the study of medicine at 72 and practiced for several years, dying in the harness. A. J. Huntington was acting professor of classics till he was 82. Mrs. A. D. T. Whitney published her twenty-seventh volume at the age of 80, etc.