No sooner did the Greeks turn their attention to the sciences which had originated in Egypt and Babylonia than the characteristic intellectual quality of the Hellenic genius revealed itself. Thales (640-546 B.C.), who is usually regarded as the first of the Greek philosophers, was the founder of Greek geometry and astronomy. He was one of the seven "wise men" of Greece, and might be called the Benjamin Franklin of antiquity, for he was interested in commerce, famous for political sagacity, and honored for his disinterested love of general truth. His birthplace was Miletus, a Greek city on the coast of Asia Minor. There is evidence that he acquired a knowledge of Babylonian astronomy. The pursuit of commerce carried him to Egypt, and there he gained a knowledge of geometry. Not only so, but he was able to advance this study by generalizing and formulating its truths. For the Egyptians, geometry was concerned with surfaces and dimensions, with areas and cubical contents; for the Greek, with his powers of abstraction, it became a study of line and angle. For example, Thales saw that the angles at the base of an isosceles triangle are equal, and that when two straight lines cut one another the vertically opposite angles are equal. However, after having established general principles, he showed himself capable of applying them to the solution of particular problems. In the presence of the Egyptian priests, to which class he was solely indebted for instruction, Thales demonstrated a method of measuring the height of a pyramid by reference to its shadow. And again, on the basis of his knowledge of the relation of the sides of a triangle to its angles, he developed a practical rule for ascertaining the distance of a ship from the shore. The philosophical mind of Thales laid hold, no doubt, of some of the essentials of astronomical science. The particulars usually brought forward to prove his originality tend rather to show his indebtedness to the Babylonians. The number of days in the year, the length of the synodic month, the relation of the sun's apparent diameter to the ecliptic, the times of recurrence of eclipses, were matters that had long been known to the Babylonians, as well as to the Chinese. However, he aroused great interest in astronomy among the Greeks by the prediction of a solar eclipse. This was probably the eclipse of 585 B.C., which interrupted a fierce battle between the Medes and the Lydians. The advice of Thales to mariners to steer by the Lesser Bear, as nearer the pole, rather than by the Great Bear, shows also that in his astronomical studies as in his geometrical he was not indifferent to the applications of scientific knowledge.