From Martin Pettinger, Keymer, West Sussex, UK
I think Mark Pickin is wrong to conclude that Stone Age seafarers wouldn’t venture out to sea unless they could see indications of land ahead. Stone Age Polynesians travelled thousands of miles between islands, navigating by wave patterns and other means. Similarly, early Viking seafarers are known to have found Iceland, Greenland and later the Azores, all of which are far out of sight of other land (Letters, 14 March
