The Brahmans seem to have made some use of astrology in working their feats of magic. Damis at any rate said that when Apollonius bade farewell to the sages, Iarchas made him a present of seven rings named after the planets, which he wore in turn upon the appropriate days of the week.[1164] Perhaps, too, the seven swords of adamant which Iarchas had rediscovered as a child had some connection with the planets.[1165] Moeragenes ascribed four books on foretelling the future by the stars to Apollonius himself, but Philostratus was unable to find any such work by Apollonius extant in his day.[1166] And unless it be an allusion to Chaldeans which we have already noted, there is no further mention of astrology in Philostratus’s _Life_—a rather remarkable fact considering that he wrote for the court of Septimius Severus, the builder of the Septizonium. [Sidenote: Interest in natural science.] The philosopher Euphrates, who is represented by Philostratus as jealous of Apollonius, once advised the emperor Vespasian, when Apollonius was present, to embrace natural philosophy—or a philosophy in accordance with natural law—but to beware of philosophers who pretended to have secret intercourse with the gods.[1167] There was justification in the latter charge against Apollonius, but it should not be assumed that his mysticism rendered him unfavorable to natural science. On the contrary he is frequently represented by Philostratus as whiling away the time along the road by discussing with Damis such natural problems as the delta of the Nile or the tides at the mouth of the Guadalquivir. He was especially interested in the habits of animals and the properties of gems. Vespasian was fond of listening to “his graphic stories of the rivers of India and the animals” of that country, as well as to “his statements of what the gods revealed concerning the empire.”[1168] Some of the questions which Apollonius put to the Brahmans concerned nature.[1169] He asked of what the world was composed, and when they said, “Of elements,” he asked if there were four. They believed, however, in a fifth element, ether, from which the gods had been generated and which they breathe as men breathe air. They also regarded the universe as a living animal. He further inquired of them whether land or sea predominated on the earth’s surface,[1170] and this same attitude of scientific inquiry and of curiosity about natural forces and objects is frequently met in the _Life_. [Sidenote: Natural law or special providence?]