his fiftieth
Note from 'Visits Sheffield' chapter from 'Memoirs Of My Life And Writing' by Gibbon

See Buffon, Supplément à l'Histoire Naturelle , tom. vii, PP. 158-64: Of a given number of new-born infants, one half, by the fault of nature or man, is extinguished before the age of puberty and reason — a melancholy calculation!