India was still a distant land of wonders and home of magic to the minds of medieval men, as it had been in the _Life of Apollonius of Tyana_, and as even to-day many westerners are credulous concerning its jugglers, fakirs, yogis, and theosophists. So William of Auvergne, bishop of Paris, writing in the first half of the thirteenth century, states that feats of magic are very seldom wrought in the Europe of his time. For one thing, as Origen and other early church fathers had already explained, the demons since the coming of Christ to earth had largely ceased their magical activities in Christian lands. But another reason was that the materials for working natural magic, the gems and herbs and animals with marvelous virtues, were seldom found in European lands. In India and other countries adjacent to it, on the contrary, such materials were abundant. Hence natural magic still flourished there and it was a land of many experimenters and of skilful marvel-workers.[723] Similarly Albertus Magnus, discussing the marvelous powers of astrological images, states that the best gems upon which to engrave them are those from India.[724] Costa ben Luca says in his work on physical ligatures that doctors in India are firm believers in the efficacy of incantations and adjurations; and about 1295 Peter of Abano speaks in his _Phisionomia_ of the wise men of India as prolix on astrological themes. Medieval geomancies, too, often claim a connection with India.[725] [Sidenote: India’s real contribution to knowledge.] It should also be kept in mind, however, that medieval men believed that they derived from India learning which seems to us even to-day as sound and useful as it did to them then; for example, the Hindu-Arabic numerals.[726] Leonardo of Pisa, the great arithmetician of the early thirteenth century, tells us in the preface to his _Liber Abaci_[727] how, summoned as a boy to join his father who was a customs official at a trading station in Algeria, he was introduced to the art of reckoning “by a marvelous method through the nine figures of the Indians.” Thus we see that India’s marvels were not always false. Later he traveled in Egypt, Syria, Greece, Sicily, and Provence and studied their various methods of reckoning, but vastly preferred the Indian method to all others, returned to a more intensive study of it, and developed it further by additions from Euclid and contributions of his own. Not always, it is true, were medieval mathematicians as favorable to Indian methods as this. Jordanus Nemorarius in one passage characterizes an Indian theorem as “nothing but mere credulity without demonstration.”[728] But to return to the natural marvels of India. [Sidenote: The legend of Prester John.]