How does Cosimo die?

One day, they find him perched high in a tree, nearly rigid and non-responsive. They send up a doctor to no avail, and then a priest. Nothing anyone can do moves Cosimo from that spot, until the aeronauts come. Coming into view of the whole group is a, elaborately decorated hot-air balloon. When the wind catches it and threatens to take it out of control, the Englishmen inside lower it to get it out of the gust, and then Cosimo, agile as a boy, leaps from his perch on the tree and grabs hold of the anchor rope. Before anyone can react, he drops from there into the sea below.