What does lago see cassio do that delights himw

I think this particular scene has Cassio praising Desdemona. Just as every character has their own manner of speech and expression, Cassio has a very polished, courtly way of speaking, especially of ladies. He describes Desdemona as one who "excels the quirks of blazoning pens"; he calls her "divine Desdemona." Cassio has no love interest in Desdemona but his praises will work into Iago's plan for convincing Othello that there is something going on between the two.