Cesi expanded the ranks of the Academy, recruiting Giambattista della Porta himself in 1610 and Galileo Galilei in 1611. Cesi's letter to Galileo of 21/7/1612 mentioned Kepler's ellipses. Cesi's Academy published Galileo's Istoria e dimostrazione intorno alle macchie solari (Letters on Sunspots) in 1613, The Assayer in 1623, and also had a hand in defending Galileo in his controversies with establishment leaders and ecclesiastical authorities.