that every bit of soil on the surface of the globe must have passed through their bodies many times. They were discovered to work mainly by night, when hundreds may with care be discerned, with tails fixed in their burrows, prowling round in circles, rapidly retreating into holes, and strongly resisting efforts to extract them. It was found … that they have no sense of hearing, but a most remarkable sensitiveness to vibrations of the earth or even to contact with air in motion.
This book which, like the others achieved a great and unexpected popularity, left Darwin exhausted. "I feel so worn out that I do not suppose I shall ever again give reviewers trouble," he wrote Hooker. Yet for several months he worked on, not with enthusiasm nor with the hope of carrying out another large project, yet with interest. In March and April, 1882, he felt poorly, and the action of his heart became so weak that he was unable to climb the stairs. On April 18 he was well enough to examine a specially interesting plant which had been brought him, but on the following day he died.
