Only prejudice, and a trick of the Mercator projection, prevents us from recognizing the enormity of the African continent. Covering nearly twelve million square miles, Africa is almost as large as North America and Europe combined. It is nearly twice the size of South America. As we mistake its dimensions, we also mistake its essential nature: the Dark Continent is mostly hot desert and open grassy plains.

In fact, Africa is called the Dark Continent for one reason only: the vast equatorial rain forests of its central region. This is the drainage basin of the Congo River, and one-tenth of the continent is given over to it-a million and a half square miles of silent, damp, dark forest, a single uniform geographical feature nearly half the size of the continental United States. This primeval forest has stood, unchanged and unchallenged, for more than sixty million years.

Even today, only half a million people inhabit the Congo Basin, and they are mostly clustered in villages along the banks of the slow muddy rivers that flow through the jungle. The great expanse of the forest remains inviolate, and to this day thousands of square miles are still unexplored.

This is true particularly of the northeastern corner of the Congo Basin, where the rain forest meets the Virunga volcanoes, at the edge of the Great Rift Valley. Lacking established trade routes or compelling features of interest, Virunga was never seen by Western eyes until less than a hundred years ago.

The race to make “the most important discovery of the 1980s” in the Congo took place during six weeks of 1979. This book recounts the thirteen days of the last American expedition to the Congo, in June, 1979-barely a hundred years after Henry Morton Stanley first explored the Congo in 1874-77. A comparison of the two expeditions reveals much about the changing-and unchanging-nature of African exploration in the intervening century.