So his enemies busily employed themselves in collecting evidence against him. They laid their complaints before the Inquisition of Rome, and on the occasion of paying a visit to that city, he was summoned before that tribunal which has been the shame and the reproach of the Catholic Church. It was a tribunal utterly incompetent to sit upon his case, since it was ignorant of science. In 1615 it was decreed that Galileo should renounce his obnoxious doctrines, and pledge himself neither to defend nor publish them in future. And Galileo accordingly, in dread of prison, appeared before Cardinal Bellarmine and declared that he would renounce the doctrines he had defended. This cardinal was not an ignorant man. He was the greatest theologian of the Catholic Church; but his bitterness and rancor in reference to the new doctrines were as marked as his scholastic learning. The Pope, supposing that Galileo would adhere to his promise, was gracious and kind. But the philosopher could not resist the temptation of ridiculing the advocates of the old system. He called them "paper philosophers." In private he made a mockery of his persecutors. One Saisi undertook to prove from Suidas that the Babylonians used to cook eggs by whirling them swiftly on a sling; to which he replied: "If Saisi insists on the authority of Suidas, that the Babylonians cooked eggs by whirling them on a sling, I will believe it. But I must add that we have eggs and slings, and strong men to whirl them, yet they will not become cooked; nay, if they were hot at first, they more quickly became cool; and as there is nothing wanting to us but to be Babylonians, it follows that being Babylonians is the true cause why the eggs became hard." Such was his prevailing mockery and ridicule. "Your Eminence," writes one of his friends to the Cardinal D'Este, "would be delighted if you could hear him hold forth in the midst of fifteen or twenty, all violently attacking him, sometimes in one house, and sometimes in another; but he is armed after such a fashion that he laughs them all to scorn." Galileo, after his admonition from the Inquisition, and his promise to hold his tongue, did keep comparatively quiet for a while, amusing himself with mechanics, and striving to find out a new way of discovering longitude at sea. But the want of better telescopes baffled his efforts; and even to-day it is said "that no telescope has yet been made which is capable of observing at sea the eclipses of Jupiter's satellites, by which on shore this method of finding longitude has many advantages."