Before leaving this period it is worth remarking how commercial activity had not only developed within, but had circumscribed the European area. The Arabs, penetrating eastward into Asia, came in contact with traders from north and western Europe using a route which, from the eighth century, passed “from India through Novgorod to the Baltic; and Arab coins found in Sweden prove how closely the enterprise of the Arabs and the Northmen intertwined” (H. R. Mill). Thus ways were prepared for the advancement of geographical knowledge when the science should emerge from its stagnation. CHAPTER IV. THE MEDIÆVAL RENASCENCE It was, in fact, a desire to extend both commerce and Christian religion into the far eastern lands which led to the rescue of geographical study from the evil state into which it had fallen. The Crusades form a group of incidents of no less geographical than of historical importance. Apart from their religious significance, they were undertaken with the object of discovering new routes by which the wealth of the east could be brought into commercial exchange with that of the west; and in connection with their religious significance they gave rise to a period of Christian missionary endeavour in the east. Both movements worked together to bring about the result of a discovery of Asia, so far as Europe was concerned, only less novel and important than the discovery of the New World by Columbus and his successors. Of the many travellers whose records assisted in this discovery a few may be mentioned as examples. The first whose journeys resulted in a noteworthy addition to knowledge of the Mongol Empire was Joannes de Plano Carpini, an Italian of Umbria, who led a catholic mission sent in 1245 by Pope Innocent IV to the Mongols shortly after their great invasion of eastern Europe. He was followed in 1253–55 by William of Rubruquis, a Franciscan, who was sent to Tartary by King Louis IX, and whose account is in many respects more valuable than that of Carpini. We may turn aside here to remark that the great philosopher, Roger Bacon (_c._ 1214–94), freely quoted Rubruquis in the geographical section of his _Opus Majus_. This work, and that of Albertus Magnus of Swabia (_c._ 1206–80), the student of Aristotle, exemplify the revival of interest in geographical theory along lines not dictated by Christian in opposition to pagan doctrines. Bacon revived Aristotle’s opinions as to the spherical form of the earth. He held that the sea did not cover three quarters of the globe, and that there must needs be lands unknown, to the south, east, and west of the known world, from which they must be separated only by narrow waters.