Tuesday, September 20, 1519. The sails fill with breeze. . . . The round world awaits its conqueror. He will reveal to man the nature of man's planet; he will perish; he will live forever."" You immediately recognize the screedish pen of the tireless Robert Silverberg, here introducing the simple history of the first six circumnavigations -- ""the grandest maritime adventure."" Quoting frequently from contemporary accounts, Silverberg reconstructs the voyages of Magellan, Drake, Cavendish, and three Dutch explorers, Noort, Spilbergen, and Le Maire; he offers no new research and his analyses of the impact or importance of each of these ""miracles of seamanship"" can only be termed nugatory -- Drake's gave ""psychological impetus"" to England's expanding sea power; Noort's expedition of ""purely symbolic"" value to the Dutch; etc. But like his many other histories, this has that ruthless readability and insouciant mindlessness which appeal so well to the lay audience Silverberg caters to.