eral books, and in 1879 he supervised the publication of an English version of Dr. Ernst Krause's Life of Erasmus Darwin, adding a sketch of the poet-evolutionist’s habits and character. But people were too much interested in the ideas of a living Darwin to devote much thought to those of a dead member of the same family, and fewer than a thousand copies of the book sold.
In 1881 the aged naturalist published his last book, The Formation of Vegetable Mould, Through the Action of Worms. More than forty years before he had written a preliminary sketch of the subject, and in December of the year he moved to Down he had begun an experiment which was to contribute greatly to the study. Twenty-nine years later, November, 1871, the experiment was completed. Darwin proved that bits of chalk and of harder rock could, in a period of three decades, be buried more than half a foot by the action of earthworms alone. Observations on the buried ruins of Roman towns of Britain showed that their condition was due largely to the action of these same earthworms, which year after year brought earth to the surface in the form of castings. Of the further work in this problem Mr. Brittany says:
