38 A TROPICAL DEPENDENCY air, and all created bodies are stable on its surface, the earth drawing to itself all that is heavy in the same way as a magnet attracts iron. The terrestrial globe is divided into two equal parts by the equinoctial line. The circumference of the earth is divided into 360 degrees each of 25 parasangs. This is the Indian calculation. . . . From the equinoctial line to each pole there are 90 degrees, but there is no habitable land farther north than the 64th degree." The earth, he says elsewhere, is essentially round, but not of a perfect rotundity, being somewhat depressed at the poles. His description of the countries upon the earth, including England to the west and China to the east, is extraordinarily full, and in many essential particulars remains accurate to the present day. America alone appears to have been unknown to the Arabs, and when we remember that modern Europe had to wait for the journey of Magellan round the world in the opening years of the sixteenth century to be quite sure of the shape of the globe, we must admit that in the learning of the Arabs of Spain, Negroland had sources of information far purer than any of which England at that time could boast.

In every branch of science the theoretic conquests of the Arabs gave practical results. Spectacles and telescopes resulted from their study of optics. Ebn Junis, the astronomer, was the first to apply the pendulum about the year 1000 to the measure of time, and from his abstruse studies in astronomy clocks became a domestic possession. The use of the astrolabe and the compass, revived again at a later period in Europe, were common to Arab navigation. Gunpowder has already been mentioned as a result of chemistry, and military science was revolutionised by the introduction of artillery and firearms. Improvement in agriculture and the introduction and acclimatisation of new plants were an even more important result of the same study, combined with that of botany, to which the Arabs were passionately addicted. Studies in the effects of drugs and the nature of plants were the basis of their medicine,