Harrison used both of Leland's accounts of the Scilly Isles, Itinerary I, 190-1, 318, but principally the former. He also supplemented their meagre details from other sources. The shape of the Scilly Isles, and the names of most of the individual islands, he presumably found in Reyner Wolfe's map (Leland altogether names only nine islands, or groups of islets), but he must have taken some of his information from elsewhere, for instance his comments on the islands' produce and economy.