In Science, too, the debt of Europe to India has been considerable. There is, in the first place, the great fact that the Indians invented the numerical figures used all over the world. The influence which the decimal system of reckoning dependent on those figures has had not only on mathematics, but on the progress of civilisation in general, can hardly be over-estimated. During the eighth and ninth centuries the Indians became the teachers in arithmetic and algebra of the Arabs, and through them of the nations of the West. Thus, though we call the latter science by an Arabic name, it is a gift we owe to India. In Geometry the points of contact between the Çulva Sutras and the work of the Greeks are so considerable, that, according to Cantor, the historian of mathematics, borrowing must have taken place on one side or the other. In the opinion of that authority, the Çulva Sutras were influenced by the Alexandrian geometry of Hero (215 B.C.), which, he thinks, came to India after 100 B.C. The Çulva Sutras are, however, probably far earlier than that date, for they form an integral portion of the Çrauta Sutras, and their geometry is a part of the Brahmanical theology, having taken its rise in India from practical motives as much as the science of grammar. The prose parts of the Yajurvedas and the Brahmanas constantly speak of the arrangement of the sacrificial ground and the construction of altars according to very strict rules, the slightest deviation from which might cause the greatest disaster. It is not likely that the exclusive Brahmans should have been willing to borrow anything closely connected with their religion from foreigners. Of Astronomy the ancient Indians had but slight independent knowledge. It is probable that they derived their early acquaintance with the twenty-eight divisions of the moon's orbit from the Chaldeans through their commercial relations with the Phoenicians. Indian astronomy did not really begin to flourish till it was affected by that of Greece; it is indeed the one science in which undoubtedly strong Greek influence can be proved. The debt which the native astronomers always acknowledge they owe to the Yavanas is sufficiently obvious from the numerous Greek terms in Indian astronomical writings. Thus, in Varaha Mihira's Hora-çastra the signs of the zodiac are enumerated either by Sanskrit names translated from the Greek or by the original Greek names, as Ara for Ares, Heli for Helios, Jyau for Zeus. Many technical terms were directly borrowed from Greek works, as kendra for kentron, jamitra for diametron. Some of the very names of the oldest astronomical treatises of the Indians indicate their Western origin. Thus the Romaka-siddhanta means the "Roman manual." The title of Varaha Mihira's Hora-çastra contains the Greek word hora.