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———. 1864. “On the Secular Cooling of the Earth.” Transactions of the Royal Society of Edinburgh, 23, 167. From reprint in Mathematical and Physical Papers, 3, p. 295, 1890.

———. 1868. “On Geological Time,” Address delivered before the Geological Society of Glasgow, February 27, 1868. Popular Lectures and Addresses, vol. 2, p. 10.

———. 1891–94. Popular Lectures and Addresses, 3 vols. (London: Macmillan and Co.).

———. 1895. “The Age of the Earth.” Nature, 51, 438.