ESSAY VII OF THE DURATION OF HUMAN LIFE The active and industrious portion of the human species in civilized countries, is composed of those who are occupied in the labor of the hand, and in the labor of the head. The following remarks expressly apply only to the latter of these classes, principally to such as are occupied in productive literature. They may however have their use to all persons a considerable portion of whose time is employed in study and contemplation, as, if well founded, they will form no unimportant chapter in the science of the human mind. In relation to all the members of the second class then, I should say, that human life is made up of term and vacation, in other words, of hours that may be intellectually employed, and of hours that cannot be so employed. Human life consists of years, months and days: each day contains twenty-four hours. Of these hours how many belong to the province of intellect? "There...