persons having reached the age of eighteen years, there die 944 before they are seventy years old; 42 between seventy and seventy-nine; 13 between eighty and eighty-nine; and one between ninety and ninety-nine. The divergencies between the two groups are very evident.
If we limit our investigations to a purely intellectual domain—that is, if we confine the examination to scientific and literary men and artists—we shall find that the chances of life are greatest with the first and least with the last. A. Quetelet has, in his "Anthropometric," made a comparison on this point between the most famous men of antiquity and of modern times, and has found that the mean life of fourteen most illustrious artists was fifty-nine years and four months; of twenty-four literary men, sixty-five years and six months; and of twenty-two scientific men and philosophers, seventy-three years and eleven months. On our own side, we have made a selection of the twenty-three most celebrated astronomers, and have found their average term of life to be seventy-one years and eleven months. The duration of life among these different classes of men of intellectual life varies, as we have seen, when we pass from one to the other. The variations depend both on external conditions peculiar to each of them, and upon the objects of their labors and studies. The two causes are in fact connected, the first proceeding naturally from the second.
Professor P. Riccardi, in his "Biblioteca Matematica Italiana," gives a table of the average life of the mathematicians of Italy, in the order of their fame. He has arranged his mathematicians in four categories, comprising: 1. The three most illustrious names (Archimedes, Galileo, and Lagrange). 2. Forty-seven mathematicians of great reputation. 3. Fifty of the second rank. 4. Three hundred and eighty of the third rank. The average duration of life in these categories of mathematicians was—1. Seventy-six years and eight months. 2. Sixty-nine years and five months. 3. Sixty-six years and four months. 4. Sixty-five years and ten months.
The fame of a scientific man being generally in proportion to the industry with which he works, we may draw our inferences from these facts as to the relations between activity and duration of life.
Another interesting fact has been brought out in our researches for this article. The excitement of the life of our age and the consequent diminution of its length have been frequently spoken of. We do not live as long as formerly, it is said, but we live more rapidly. The latter hypothesis may be true, but the former one is certainly false, as statistics have demonstrated for the present century. In Belgium, among other countries, the mean of life, which, during the period from 1841 to 1845, was thirty-one years and three months, was lengthened to thirty-three years in the lustrum from 1871 to 1875. A similar difference has been observed in other countries. Data for comparison are scarce for centuries previous to the present one, but our statistics of the lives of astronomers may give us some information on this point.
