One snowy February night in a friend’s New York apartment, Thurston Clarke spun an old globe. His right index finger traced its center line. Bored with winter, yielding to a travel lust that had often directed his life, Clarke hatched his scheme of following this imaginary dividing line between the northern and southern halves of Earth from end to end.

Preparations for the trip were enormous. Gear had to be bought, inoculants by the score shot into sore arms and buttocks, pills and potions organized in a backpack of limited capacity, and visas obtained, even from Sao Tome, which prohibits tourism. Decisions loomed: in which direction to proceed (west-east), where to start (the equatorial city of Macapa, Brazil), what transportation to use (mostly airplanes), whether to break a trip that necessitated traversing South America, Africa, and Asia (only when airline routes demanded it).

Clarke’s book rambles like his journey. It is comfortable to read, and fascinating as well. It presents an intermixture of events such as Clarke’s visiting Albert Schweitzer’s hospital at Lambarene or coming to know Edward, an orphaned street person in Mbandaka; of such oddments of information as the fact that equatorial nations are trying to extend their sovereignty 22,300 miles into space, the height at which equatorial communications satellites hover; of the superlatives equatorial things require--the largest rats, smelliest fruits, widest river, longest snake, greatest stretch of burned-out virgin forest.

The journey ends in South America, where Clarke visits the Equatorial Museum near Quito, Ecuador, a country named for the thin imaginary line upon which, with infrequent deviations, he has balanced himself for over three years. He completes his trip in Macapa, the equatorial seaport visitors rarely come to a second time.