As was the case in the other branches of natural history already noticed, the Greeks knew much more about geology than did the nations of the rest of Europe, subsequently, for nearly seventeen hundred years. The first recorded teacher of the ancient history of the earth was Pythagoras, who was born on the island of Samos, about the year 570 B.C. By his mother’s side he was connected with the principal families of the island, and his father appears to have been a Phœnician or a Tyrrhenian of Lemnos. There is nothing known about his childhood, and it is evident that he studied under the great philosophers of his age in Greece. But he wanted further information, and therefore travelled into Egypt, and thence into Chaldæa. Polycrates, the ruler of the island in which Pythagoras was born, appears to have assisted him with the Egyptians by introductions. The traveller noticed not only the habits and customs of the people he visited, but also the aspect of the countries, and the method by which nature wore the earth, and produced changes on the surface of the ground. He appears to have been much struck with the periodical nature of many natural events, such as the succession of the seasons, the time of rain and inundation, and of great heat, and of all the common examples with which everyone is familiar at the present day. Returning home he soon became aware that he could not teach, unreservedly, what he had learned and discovered during his travels, for fear of Polycrates, and he left the island. Finally he settled at Croton, in southern Italy, and he appears to have chosen the locality, in order to propagate his moral and political, as well as scientific opinions. Unfortunately, this ardent scholar and teacher did not write any books, but left that task to his pupils and successors, so that much good sense is mixed with much nonsense in the so-called doctrines of Pythagoras which came from them. Some of his opinions are very remarkable and striking, and he introduced into his own country the statements of the Eastern nations, that there has been a gradual deterioration of the human race from an original state of virtue and happiness. But his principal work regarding the earth has descended to us through the poet Ovid, and it is most interesting. Pythagoras insisted that there was a perpetual and gradual system of change, inherent in the earth. This idea, which came into his mind from the results of observation, he did not apply to very remote ages, or to what is now called the ancient history of the globe. He simply insisted on modern changes. Really this limiting of his thought was in the true scientific spirit, and he dealt with what was true and proveable so far as he was concerned. It might be supposed that the present changes cannot come within the studies of the geologist, but they really do so, because, as will be noticed further on in considering the life of Hutton, the past