The maintenance of this infidel stronghold in the heart of Christian Europe was a standing reproach to the Papacy; and the horror of the clergy was aggravated by the knowledge that churches had been demolished to supply it with building materials; that the revenues of rich and populous districts were diverted through its agency from the coffers of the cathedral and the monastery; that it enjoyed exclusive and valuable commercial privileges; and that, worst of all, it was able at a moment’s notice to furnish more than twenty thousand well-equipped, valiant, and incorruptible soldiers to the armies of the Emperor. The patronage of letters, which distinguished this accomplished sovereign, is not the least of his titles to renown. No prince ever sought out books and manuscripts with greater assiduity, or more strenuously endeavored, by the bestowal of scholastic honors and pecuniary emoluments, to attract the learned to his court. Nationality, creed, partisanship, feudal enmity, private grudges, were alike forgotten in the friendly contest for literary pre-eminence. In the royal antechambers, in the halls of the University, no student was entitled to precedence, save only through his established claim to mental superiority. The incessant rivalry of many acute and highly cultivated intellects, stimulated by rewards and unhampered by restrictions, was productive of results most important for the revival of letters and the future benefit of humanity. Great advances were made in all departments of knowledge,--chemistry, natural history, botany, poetry, mathematics. The famous scholar, Michael Scott, whose rare attainments contemporaneous ignorance attributed to magic, and whose simple tomb in Melrose Abbey awakens to-day the veneration of every educated and appreciative traveller, was employed by the Emperor as a translator of the classics, and carried to Palermo vast stores of learning acquired in the schools of the Spanish Moslems. Theodore, called “The Philosopher,” published treatises on geometry and astrology; John of Palermo wrote on arithmetical problems; Leonardo Fibouacci brought to the general notice of Europe the science of algebra as known and used in modern schools; the versatile Pietro de Vinea, statesman, jurist, orator, amused his leisure in the composition of the first Italian lyric poetry, and of epistolary correspondence unsurpassed, in any age, for perspicuity, ease, and elegance of diction. Frederick himself wrote amorous sonnets, and published in Latin a work on hawking and birds of prey, which is even now an authority on the subject. The apocryphal book, De Tribus Impostoribus, an alleged compendium of blasphemy and vileness, attributed to him by the clergy of the Middle Ages, is now known to have been an invention of ecclesiastical malice to blacken a character only too vulnerable to such attacks. At the Sicilian court was formed that melodious and graceful idiom afterwards employed with such success by Petrarch,