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James Croll. Portrait of James Croll (1821-90), Scottish geologist. Croll's scientific knowledge was largely self-taught & during 1867-81 he served with the Scottish geological survey. From 1864 he studied the possible causes of ice ages. Using the work of Adhemar he concluded that the eccentricity (deviation from a circle) of the Earth's orbit varied over time. He thought that an ice age occurred when the Earth was farthest from the Sun at times of high eccentricity. Croll also argued that ocean currents and the distribution of land could also affect climates. He argued that the Earth was far younger than it actually is; this contradicted Lyell's uniformitarian theories.
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