The centre of interest now changes to Babylonia. Here, in the year 219, Abba Areka, or Rab (175-247), founded the Sura academy, which continued to flourish for nearly eight centuries. He and his great contemporary Samuel (180-257) enjoy with Jochanan the honor of supplying the leading materials of which the Talmud consists. Samuel laid down a rule which, based on an utterance of the prophet Jeremiah, enabled Jews to live and serve in non-Jewish countries. "The law of the land is law," said Samuel. But he lived in the realms of the stars as well as in the streets of his city. Samuel was an astronomer, and he is reported to have boasted with truth, that "he was as familiar with the paths of the stars as with the streets of Nehardea." He arranged the Jewish Calendar, his work in this direction being perfected by Hillel II in the fourth century. Like Simlai, Rab and Samuel had heathen and Christian friends. Origen and Jerome read the Scriptures under the guidance of Jews. The heathen philosopher Porphyry wrote a commentary on the Book of Daniel. So, too, Abbahu, who lived in Palestine a little later on, frequented the society of cultivated Romans, and had his family taught Greek. Abbahu was a manufacturer of veils for women's wear, for, like many Amoraim, he scorned to make learning a means of living, Abbahu's modesty with regard to his own merits shows that a Rabbi was not necessarily arrogant in pride of knowledge! Once Abbahu's lecture was besieged by a great crowd, but the audience of his colleague Chiya was scanty. "Thy teaching," said Abbahu to Chiya, "is a rare jewel, of which only an expert can judge; mine is tinsel, which attracts every ignorant eye." It was Rab, however, who was the real popularizer of Jewish learning. He arranged courses of lectures for the people as well as for scholars. Rab's successor as head of the Sura school, Huna (212-297), completed Rab's work in making Babylonia the chief centre of Jewish learning. Huna tilled his own fields for a living, and might often be met going home with his spade over his shoulder. It was men like this who built up the Jewish tradition. Huna's predecessor, however, had wider experience of life, for Rab had been a student in Palestine, and was in touch with the Jews of many parts. From Rab's time onwards, learning became the property of the whole people, and the Talmud, besides being the literature of the Jewish universities, may be called the book of the masses. It contains, not only the legal and ethical results of the investigations of the learned, but also the wisdom and superstition of the masses. The Talmud is not exactly a national literature, but it was a unique bond between the scattered Jews, an unparallelled spiritual and literary instrument for maintaining the identity of Judaism amid the many tribulations to which the Jews were subjected.