Close to this group, but farther to the East, the central group also concerns us, for some of its representatives who now inhabit the boundaries of Europe made repeated incursions into Europe in various directions. In the plains lying between the River Irtish and the Caspian Sea live the Kirghiz-Kazaks, and in the Tien-Shien Mountains the Kara-Kirghiz, who have preserved many ancient Old Turkish customs, and seem to have been only slightly Mohammedanised. The Usbegs and the Sartis of Russian Turkistan, on the other hand, have been more or less Iranised. Finally, on the banks of the Volga are to be found the Tatars of European Russia. Among them the Tatars of Kazan, who are descended from the Kiptchaks, came to the banks of the Volga in the thirteenth century and mingled with the Bulgars. These Tatars differ from the Tatars of Astrakhan, who are descendants of the Turco-Mongols of the Golden Horde, and are connected with the Khazars, and from the Nogaïs of the Crimea, who are Tatars of the steppes who more or less inter-married with other races—the Tatars of the Tauris coast being the hybrid descendants of the Adriatic race and the Indo-Afghan race. They are to be found near Astrakhan and in the Caucasus Mountains, and even, perhaps, as far as Lithuania, “where, though still being Mohammedans, they have adopted the language and costume of the Poles.”[1] * * * * * The invasion of Europe by the Turks appears as the last great ethnic movement that followed the so-called period of migration of peoples (second to sixth centuries A.D.) and the successive movements it entailed. Let us consider only the migrations of those who concern us most closely, and with whom the Turks were to come into contact later on. First the Slavs spread westward towards the Baltic and beyond the Elbe, and southward to the valley of the Danube and the Balkan Peninsula. This movement brought about the advance of the Germans towards the west, and consequently the advance of the Celts towards Iberia and as far as Spain. Owing to the invasion of the Huns in the fifth century and in the sixth of the Avars, who, after coming as far as Champagne, settled down in the plains of Hungary and the territories lying farther to the south which had already been occupied by the Dacians for several centuries, the Slavs were cut into two groups. About the same time, the Bulgars came from the banks of the Volga and settled on the banks of the Danube.