In the spring of 1803, I, Samuel Walker, and my Uncle William were sent by President Jefferson into the wilderness between the Ohio River and the Gulf of Mexico to find specimens of the animal called the giant sloth."" So begins this moderately diverting, half-farcical adventure journal--which follows Samuel (a would-be painter) and Uncle William (a renowned botanist) as they search for ""megatherium,"" the great beast that will prove to Europe that the New World is no slouch in the fauna department. (Says Tom Jefferson: ""These lies must be extinguished so that no one will dare mistake America for a land of stunted feeblings!"") The trek begins idyllically enough, with the two men floating down the Ohio on a keelboat. Very soon, however, the usual picaresque calamities commence. The Walkers are taken captive by a loathsome, desperate pirate trio: Capt. Bilbo, his ""odious black-eyed dwarf,"" and his nymphomaniacal, harelipped daughter (whose below-the-neck features suit Samuel quite well in the dark). After a near-fatal run-in with hostile Indians, the Walkers escape from both sets of captors, thanks to some hallucinogenic herbs--only to wind up in Babylon, Ky., a ""squalid bit of barbarism."" (By comparison, Cincinnati across the river is ""a very clean village."") Then, in the novel's rather static central section, Samuel and William stumble upon the ""incredible floating palace"" of the enigmatic M. LeBoeuf--who has a sexually restless wife (she'll entrap William in some zipless action), a half-wit ward called Lou-Lou (could he be the lost Dauphin of Francâ€š), and a vast supply of seemingly happy black slaves. (Inevitably, there'll be a flaming insurrection, complete with ""LeBoeuf's blood-smeared head impaled at the end of a twenty-foot pike,"" as the Walkers paddle safely away from the spectacle.) And, before returning safely north, the adventurers will join a traveling side-show on the Mississippi (Capt. Bilbo resurfaces), dwell for a time among the mysterious Wejun tribesmen (near the Gulf), and survive both a hurricane and the wrath of a Georgia plantation-owner. Throughout, versatile, uneven novelist Kunstler (The Wampanaki Tales. The Life of Byron Jaynes) tosses in echoes of such American-wilderness classics as Huckleberry Finn and the James Fenimore Cooper canon. (Natty Bumppo makes a few cameo appearances.) The dialogue features some anchronistic humor in exchanges of bawdy put-downs. Overall, however, this comic expedition is played relatively straight--with neither the hilarious highs nor the sophomoric lows that more wacky period frolics have achieved.