These purple patches were nothing more than the accidents of a transition period. The people as a whole was on the decline. The Jewish mind darted hither and thither, like a startled bird seeking its nest. Holland or Turkey was an inadequate substitute for Spain, if only for the reason that but a tiny fraction of the Jews had found shelter in either. The Jewish national centre must perforce coincide with the numerical centre of the dispersed people, in which, moreover, conditions must grant Jews the possibility of living undisturbed in closely compacted masses, and of perfecting a well-knit organization of social and individual life. Outside of Spain these conditions were fulfilled only by Poland, which gradually, beginning with the sixteenth century, assumed the hegemony over the Jewry of the world. This marks the displacement of the Sephardic (Spanish, in a broader sense, Romanic) element, and the supremacy of the Ashkenazic (German-Polish) element. Poland had been a resort for Jewish immigrants from Germany since the outbreak of the Crusades, until, in the sixteenth century, it rose to the position of a Jewish centre of the first magnitude. As the merchant middle class, the Jews were protected and advanced by the kings and the Szlachta. The consequent security of their position induced so rapid a growth of the Jewish element that in a little while the Jews of Poland outnumbered those of the old Jewish settlements in Occidental Europe. The numerous privileges granted the Jews, by Boleslaus of Kalish (1246), Kasimir the Great (1347-1370), Witowt (1388), Kasimir IV (1447), and some of their successors, fortified their position in the extended territory covered by Poland, Lithuania, and the Ukraine. Their peculiar circumstances in Poland left an impress upon their inner life. An intense mental activity was called forth. This activity can be traced back to German beginnings, though at the same time it is made up of many original elements. For a space Rabbinism monopolized the intellectual endeavors of the Polish Jews. The rabbi of Cracow, Moses Isserles, and the rabbi of Ostrog, Solomon Luria (d. 1572), disputed first place with the foremost rabbinical authorities of other countries. Their decisions and circular letters regarding religious and legal questions were accorded binding force. Associates and successors of theirs founded Talmud academies throughout the country, and large numbers of students attended them. Commentators upon the Talmud and expounders of classical works in Jewish theological literature appeared in shoals. Jewish printing establishments in Cracow and Lublin were assiduous in turning out a mass of writings, which spread the fame of the Polish rabbis to the remotest communities. The large autonomy enjoyed by the Polish and Lithuanian Jews conferred executive power upon rabbinical legislation. The _Kahal_, or Jewish communal government, to a certain degree invested with judicial and administrative competence, could not do