Note 20 — Chapter IX
Reading edition
Ullòa in his voyage to South-America relates, that in passing over the Deserts, Írides are frequently seen by Travellers round their own Heads as the Center of the Iris; and visible only to themselves. But what Analogy the Balloon Iris bears to them, Time and future Experiments may discover. See his “Voyage to South America, Vol. 1. Pa. 442.”