During the following year hostilities continued in the immediate neighbourhood of Frauenburg, but in the course of that summer, negotiations for peace between the Teutonic Order and the King of Poland were begun, through the mediation of the bishop. At last a truce was agreed upon for four years, during which Fabian von Losingen died, and Copernicus was again chosen administrator of the bishopric. In 1525 peace was concluded with the Teutonic Knights, Albert having consented to receive Prussia as a temporal fief from the King of Poland. It was probably on this occasion that Copernicus was selected to represent the chapter of Ermeland at the Diet at Graudenz, where the terms of peace were finally settled; and by his firmness the chapter recovered great part of the possessions which had been endangered during the war. This service to his chapter was followed by another of more widely extended importance. During the struggle, which had continued with little interruption for more than half a century, the currency had become greatly debased and depreciated; and one of the most important subjects of deliberation at the meeting at Graudenz related to the best method of restoring it. There was a great difference of opinion whether the intended new coinage should be struck according to the old value of the currency, or according to that to which it had fallen in consequence of its adulteration. To assist in the settlement of this important question, Copernicus drew up a table of the relative value of the coins, then in circulation throughout the country. He presented this to the States, accompanied by a memoir on the same subject, an extract from which may be seen in Hartknoch’s History of Prussia. Throughout the troublesome period of which we have just given an outline, Copernicus seems to have displayed much political courage and talent. When tranquillity was at length restored, he resumed the astronomical studies which had been thus interrupted by more active duties. There appears to be little doubt that the philosopher began to meditate on the ideas which led him to the true knowledge of the constitution of the solar system, at least as early as 1507. Every one, who has heard the name of Copernicus mentioned, is aware that before him the general belief was, that the earth occupies the centre of the universe; that the changes of day and night are produced by the rapid revolution of the heavens, such as our senses erroneously lead us to believe, until more accurate and complicated observation teaches us the contrary; that the change of seasons and apparent motions of the planetary bodies are caused by the revolution of the sun and planets from west to east round the earth, in orbits of various complexity, subject to the common daily motion of all from east to west.