The combatants who took the field with various writings to defend the Peripatetic school against these fresh attacks of Galileo were the professors Giorgio Corressio, Tommaso Palmerini, Lodovico delle Colombo, in 1612, and in 1613 Vincenzo di Grazia. Corressio was answered by Benedetto Castelli; but the work, which is preserved in MS. in the National Library at Florence, was not published, out of pity for his opponent who, in the meantime, had been overtaken by severe misfortune. Although professing to be a Roman Catholic, he was discovered to belong to the Greek Non-Uniat church, which entailed the loss of his professorship at the University of Pisa. Galileo intended himself to answer Palmerini, but while he was doing so Palmerini died, and not wishing to fight a dead man, he laid his reply aside. The lame objections of the other two received a brilliant refutation in a work published in 1615 by Castelli. From the original MS., however, in the National Library at Florence, which is mostly in Galileo’s handwriting, it is evident that he was the real author.[83] During the same year in which he had so alarmed the Peripatetics by the treatise on floating bodies, he was much occupied with the controversy with the Jesuit father, Scheiner, before mentioned, professor of mathematics at Ingolstadt, about the solar spots and the priority of their discovery. In three letters to Welser of Augsburg (published there in 1612) he had claimed for himself, under the pseudonym of “Apelles,” the earliest observation of these appearances, and explained them conformably to the traditional opinions. He propounded the ingenious idea that these spots were a multitude of little planets, passing over the sun’s disk as they revolved round the earth. By this clever explanation he secured the applause of all the Peripatetic school, and proclaimed himself the decided foe of Galileo. Challenged to do so by Welser, Galileo replied in three letters addressed to him, in which “Apelles” came off but poorly.[84] Galileo convincingly refuted his opponent’s explanation of the spots, and brilliantly defended his own right to the priority of their discovery by appealing to witnesses to whom he had made it known in 1610. These letters, together with Scheiner’s, were published in March, 1613, under the title “History and Explanation of the Solar Spots,”[85] with a fine portrait of Galileo, and a dedication to his illustrious friend Salviati, of the “Accadémia dei Lincei.”