Everyone has a hiking/writing gimmick these days: let's walk across Tibet, ramble through the Outback, bounce around the world on a pogo stick--and author a book about it. By contrast, Englishman Pern's (The Beach of Morning, 1984; Another Land, Another Sea) decision to tromp the Continental Divide from Mexico to Canada sounds uninspired, but his writing takes up the slack as he delivers a witty, peppy, on-target study of America's western lands. Why the Divide? Because it's ""the world's longest watershed, the backbone of an entire hemisphere, lord of nothing, servant of the great waters rising on its flanks. . ."" And because it caught his eye when thumbing through his family atlas. Typically, charmingly, Peru intertwines majestic description with a bit of tweaking the reader. Trimming his pack, he ""cut the margins off maps, the labels off clothes, my nose off to spite my face."" Reaching a mountain pass, he decides ""to direct a stream of my own personal urine directly onto the watershed. I would watch it divide, flowing east, flowing west, two momentous trickles, messengers to the far distant seas."" Pern mixes this good-natured, self-deprecating badinage with gobs of geology, natural history, local history, misadventures (he falls off a mountain in Colorado, finds himself staring into a gun barrel in Montana), and wildlife encounters (pronghorn antelope, moose, Texas horned lizards, grizzlies). Topping it all, he serves as a magnet for a carnival of American originals--talkative killers, snarling park rangers, do-it-yourself psychic explorers, kindly couples--captured in quick, insightful, sometimes hilarious sketches. An Englishman from head to toe--he brews tea on desert sands and mountain peaks--Pern's foreignness gives him just the right perspective to snare the heart of America. Then, too, he makes a superlative trail guide. An unbeatable combination.