In this case as in many others the Arab has left his impress on this science. For instance, our word cipher, and kindred words, such as decipher, ciphering, etc., are derived from the word _tsaphara, or ciphra_, the name for the 0 in the Arabic language. In experimental sciences, they originated chemistry and discovered the nature and properties of sulphuric acid, nitric acid, alcohol and many other chemical agents. From their schools of medicine may be traced such words as julep, syrup, elixir, alchemy, etc. To them we are indebted for algebra, or universal arithmetic, and in astronomy they made such advances that many constellations and stars of the first magnitude still retain the Arabic names. In geography, the Saracens made important discoveries. Hitherto mankind had been taught that the earth was a vast {37} plain, surmounted by an immense vault commonly called the sky. They were the first to prove that the earth is a vast globe, or ball; and in order to determine its size, they first ascertained on the level shore of the Red sea the exact position of the North Star. Then traveling directly north until it had attained another degree of elevation, they measured the distance between these points, and multiplying the result by three hundred and sixty (the number of degrees in a circle), they found the earth to be nearly twenty-five thousand miles in circumference. So accurate were their observations and measurements that the best calculators of recent times differ from them less than one-third of a mile. Five hundred years later the Roman pontiffs were excommunicating and torturing those who taught the rotundity of the earth. While Catholic monks were teaching, in all its absurdity, the flatness of the earth, and how it rested on a vast rock, and that rock on another and so on all the way down to the bottom(?), the Saracens were teaching geography from globes in their common schools. It cost a long struggle through several centuries, "with spiritual wickedness in high places," before the truth finally triumphed. European historians have generally given great credit to Pope Gregory for the invention and adoption of the Gregorian calendar and a more accurate method of measuring the exact length of the civil year. Yet, Gregory only adopted what had been discovered and taught by Thebit-Ben-Corrah, the Saracen astronomer, more than five hundred years before, and what Gregory himself had learned in youth while attending a Saracen university. The mariner's compass was well known to the Arabs, who probably brought it from China and introduced it to the nations of Europe. From this we may correctly infer that they were a maritime people. In fact, long before the time of Mahomet, Arabian merchants were acquainted with the Indies, and even China and the eastern coast of Africa as far south as Madagascar.