The voyages of Thor Heyerdahl across the Atlantic provide instructive examples of adventures undertaken ostensibly in search of knowledge. In The Ra Expeditions the story is told of how, in pursuit of an idea, if not of a theory, Mr Heyerdahl at a second attempt succeeded in crossing the Atlantic from Morocco to Barbados in a craft made of papyrus stems lashed together with ropes….

The account of the [first attempt and the second successful voyage] can do nothing but arouse admiration for the temerity and determination of the two crews—amateur in every respect—driven to epic achievement by the obsession of Thor Heyerdahl…. He is very careful not to claim too much, but the implication of the whole book is that Egyptians colonized America, probably by chance, and that they did it by means of papyrus craft.

It is as an adventure story that The Ra...