"Vogt was unable to test this hypothesis until late in 1940, when he persuaded the guano company to measure plankton abundance by dragging the sea at multiple locations with a fine silk net. He examined the samples with the sole tool available, a magnifying glass he had managed to acquire on a trip to Lima. Despite the crude equipment he was able to gather enough data to see what was happening. The "general tendency," he wrote, was for "falling temperature to be accompanied by increasing plankton, and vice versa"--an inverse relationship. Abrupt water-temperature rises "resulted in wholesale destruction" of plankton. Desperately hungry, the Guanays had scattered in every direction to search for food."