A former submarine commander in Britain's Royal Navy, Menzies must enjoy  doing battle. The amateur historian's lightly footnoted, heavily  speculative re-creation of little-known voyages made by Chinese ships in  the early 1400s goes far beyond what most experts in and outside of  China are willing to assert and will surely set tongues wagging.  According to Menzies's brazen but dull account of the Middle Kingdom's  exploits at sea, Magellan, Dias, da Gama, Cabral and Cook only  "discovered" lands the Chinese had already visited, and they sailed with  maps drawn from Chinese charts. Menzies alleges that the Chinese not  only discovered America, but also established colonies here long before  Columbus set out to sea. Because China burned the records of its  historic expeditions led by Zheng He, the famed eunuch admiral and the  focus of this account, Menzies is forced to defend his argument by  compiling a tedious package of circumstantial evidence that ranges from  reasonable to ridiculous. While the book does contain some compelling  claims-for example, that the Chinese were able to calculate longitude  long before Western explorers-drawn from Menzies's experiences at sea,  his overall credibility is undermined by dubious research methods. In  just one instance, when confounded by the derivation of cryptic words on  a Venetian map, Menzies first consults an expert at crossword puzzles  rather than an etymologist. Such an approach to scholarship, along with a  promise of more proof to come in the paperback edition, casts a shadow  of doubt over Menzies's discoveries. 32 pages of color illus., 27 maps  and diagrams.