MICHAEL CRICHTON

The rain forests of the world had traditionally frustrated remote-sensingtechnology. The great jungle trees spread an impenetrable canopy of vegetation,concealing whatever lay beneath. In aerial or satellite pictures, the Congo rainforest appeared as a vast, undulating carpet of featureless and monotonousgreen. Even large features, rivers fifty or a hundred feet wide, were hiddenbeneath this leafy canopy, invisible from the air.So it seemed unlikely she would find any evidence for a lost city in aerialphotographs. But Ross had a different idea: she would utilize the very vegetationthat obscured her vision of the ground. -The study of vegetation was common in temperate regions, where the foliageunderwent seasonal changes. But the equatorial rain forest was unchanging:winter or summer, the foliage remained the same. Ross turned her attention toanother aspect, the differences in vegetation albedo.Albedo was technically defined as the ratio of electromagnetic energy reflectedby a surface to the amount of energy incident upon it. In terms of the visiblespectrum, it was a measure of how “shiny” a surface was. A river had a highalbedo, since water reflected most of the sunlight striking it. Vegetation absorbedlight, and therefore had a low albedo. Starting in 1977, ERTS developedcomputer programs which measured albedo precisely, making very finedistinctions.Ross asked herself the question: If there was a lost city, what signature mightappear in the vegetation? There was an obvious answer: late secondary jungle.The untouched or virgin rain forest was called primary jungle. Primary junglewas what most people thought of when they thought of rain forests: hugehardwood trees, mahogany and teak and ebony, and underneath a lower layer offerns and palms, clinging to the ground. Primary jungle was dark and forbidding,but actually easy to move through. However, if the primary jungle was cleared byman and later abandoned, an entirely different secondary growth took over. Thedominant plants were softwoods and fast-growing trees, bamboo and thornytearing vines, which formed a dense and impenetrable barrier.But Ross was not concerned about any aspect of the jungle except its albedo.Because the secondary plants were different, secondary jungle had a differentalbedo from primary jungle. And it could be graded by age: unlike the hardwoodtrees of primary jungle, which lived hundreds of years, the softwoods ofsecondary jungle lived only twenty years or so. Thus as time went on, the61