THAMES

Of London's many pleasures, one of the most profound is a stroll along the south bank of the Thames on a warm summer evening, just as the long twilight begins to fade into night. Start at Westminster Bridge, where the Houses of Parliament cast their shimmering reflection onto the dark water's surface, and make your way east along the promenade crowded with theaters, museums, restaurants, shops and former riverine warehouses now transformed into blocks of fashionable flats. As you walk downriver, you pass more bridges -- postmodern Hungerford, utilitarian Waterloo, Victorian wrought iron Blackfriars -- while overhead the deceptively delicate wheel of the London Eye revolves, almost imperceptibly. Across the river glittering with reflected lights rises the congestion of buildings that constitutes the City of London, where Norman Foster's oversized "Gherkin" juts into the sky, dominating a cityscape more elegantly accented by the beautiful wedding-cake spire of St. Bride's, one of the churches built byChristopher Wren after the Great Fire of 1666. At the Tate Modern, formerly the Bankside Power Station, steps lead to the pedestrian Millennium Bridge, once ridiculed for its unsteadiness, but now stabilized and heavily used by residents as well as tourists. Venture across it halfway and look to your right downriver, past Southwark and London bridges, to another famous landmark, the Victorian neo-Gothic Tower Bridge. Look directly ahead, and Wren's masterpiece, St. Paul's Cathedral, fills the sky, its dome of Portland stone floodlit and glowing. This short segment of the 215-mile Thames encapsulates London's history -- a history that has centered upon its river. Peter Ackroyd, author of many novels and biographies, writes with his customary eloquence and thoroughness to tell us why. Thames is a companion to Ackroyd's London: The Biography (2001), and, as in that previous volume, he makes his subject seem so much a living entity that the term "biography" -- etymologically, "life writing" -- is apt. As a biography, Thames necessarily traces the entire course of this meandering river from its source near Cirencester, Gloucestershire (a photograph shows where it rises, guarded by a sacred ash tree, in a field called Trewsbury Mead), to the estuary beyond Gravesend where it empties into the North Sea. But the river's real historical resonance is inextricably bound up with the great city it may be said to have created, so crucial have been its waters to nearly every aspect of London life. The term biography usually implies a chronological approach, and Ackroyd's early chapters discussing the first settlements on the river and the possible Celtic root of the ancient name Thames seem to obey this principle. But, in fact, the book is organized thematically, in sections consisting of clustered short chapters on subjects such as the economic history of the river, its sacred uses, its flora and fauna and its artistic representations. As in London , Ackroyd's method in Thames is biography by accretion, building up layer upon layer of facts, figures and stories. Chapters range widely in time; a chapter on weather, for instance, tells us on the same page that the first reported frost fair -- a festival held on the ice when, unusually, the entire river froze -- was in 695, and that in the first month of 2003 the Thames Barrier closed 18 times to prevent flooding. Other chapters cover such topics as riverside pubs, sports and pleasure gardens, and the river as cesspool, dump and source of disease: The pump responsible for the 1854 cholera epidemic was traced directly to the Thames. A section entitled "The River of Death" includes a bizarre, irresistible chapter on the river's accumulation of severed heads and an account of the Thames's history of murders, suicides and accidental drownings in its dangerously cold, black water. "In the history of London crime," Ackroyd tells us, "there is not one recorded example of a criminal swimming across the river to escape from his pursuers." In the section entitled "The River of Art" devoted to painterly, musical and literary treatments -- by Canaletto, Whistler, Handel, Shelley and others -- Ackroyd's discussion of Dickens (about whom he has written a biography) strikes a similarly sinister note: "No previous writer had so well captured the lachrymose and minatory aspects of the river. It was the river of secrets, the river of mist and fog, the river of night and thus the river of mystery." Our Mutual Friend opens with Lizzie Hexam rowing a boat on a slimy, oozing Thames, while her father searches for floating corpses to snag and rifle. But Charles Kingsley's The Water Babies and Kenneth Grahame's The Wind in the Willows also make appearances in this chapter, lightening the mood considerably. Each chapter of Thames is packed with information, the result of prodigious research. (Ackroyd acknowledges his two hard-working researchers.) The sheer amount of detail -- economic, artistic, historical, political, geographical, mythological, geological, ecological, climatological, hydrological -- is dazzling, if potentially inundating. Readers may prefer to dip their toes into Thames rather than take a full-immersion plunge. Indeed, the various sections can be read independently in any sequence that appeals, probably the most satisfying approach. However you read it, Ackroyd's enthusiasm for his fascinating subject ensures that his book never become tedious. The price of Ackroyd's holistic method, however, is that breadth is bought at the expense of depth. If you'd like more information about the danger of flooding or a nuanced reading of Dickens's river-haunted prose, you must look elsewhere: This is the necessary trade-off for the abundance Ackroyd delivers. A more serious concern is that despite his tone of magisterial authority -- after all, his subtitle proclaims that this is "the" rather than "a" biography -- he does not cite his sources. Even in a book intended for general readers, the complete absence of scholarly notation and the limited bibliography are genuine shortcomings: We cannot easily follow up his research. Still, as an overview and introduction, Thames is a very satisfying read, bringing the rich, multi-dimensional history of this great, mysterious river to life. Although the ancient Greek poet Pindar is one of the seemingly few writers Ackroyd does not quote, his cryptic but evocative line could serve well as this book's epigraph: "Water is best."