This window depicts Christ's Ascension into Heaven. He is surrounded by Cherubim.
"Cherubim/cherubs are angelic beings involved in the worship and praise of God. This is one of their main responsibilities throughout the Bible. In addition to singing God's praises, they also serve as a visible reminder of the majesty, glory, holiness, and power of God and His abiding presence with His people." (Source)
For forty days after his resurrection, Jesus appeared to many people. The last time they met together, Jesus said,
"It is not for you to know the times or dates the Father has set by his own authority [for what will happen in the future]. But you will receive power when the Holy Spirit comes on you, and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth.' After He said this, He was taken up before their very eyes, and a cloud hid Him from their sight."
"When He had led them out to the vicinity of Bethany, He lifted up His hands and blessed them. While He was blessing them, He left them and was taken up into heaven."
The Irwin window was a gift of Mrs. Richard Hays in memory of Boyle Irwin (1772-1860), Elizabeth McCully Irwin (1786-1867), and Richard Hays (1815-1877).