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7.01 Mantle Dynamics Past, Present, and Future: An Introduction and Overview D. Bercovici, Yale University, New Haven, CT, USA ВЄ 2007 Elsevier B.V. All rights reserved. 7.01.1 Introduction 7.01.2 A Historical Perspective on Mantle Dynamics To some extent the development of the field of mantle dynamics is most closely linked with the history of theories of continental drift and plate tectonics. Although mantle convection was invoked to provide a driving mechanism for continental (or plate) motions, the hypothesis that the mantle flows and circulates predates even that of continental drift (see Schubert et al., 2001, chapter 1). As discussed recently by England et al. (2007), John Perry used the notion of mantle convection in 1895 to refute the estimate for the age of the Earth given by his former mentor William Thomson (Lord Kelvin). However, a great deal of progress on understanding mantle convection also comes from the general study of the physics of thermal convection, not specifically applied to the mantle. Histories of plate tectonics (or continental drift) are in abundance (e.g., Menard, 1986; Hallam, 1987) and the recent text on mantle dynamics by Schubert et al. (2001) gives an excellent summary of the history of the development of mantle convection theory in conjunction with plate tectonics. However, the historical context and personalities associated with some of the steps in this development are important to understand in terms of how the field evolved, and to some extent how science in general has been done and is done now. Thus, rather than merely repeat other historical summaries here, we will focus instead on the contributions (pertaining primarily to mantle convection) and professional and personal histories of some of the leading names in the development of the theories of thermal convection and mantle dynamics. Roughly keeping with the structure of this volume, this section concentrates on the origins of the physics, theory, and systematic experiments of convection by visiting Benjamin Thompson (Count Rumford), John William Strutt (Lord Rayleigh), and Henri Claude BeВґnard. This will be followed by reviewing the lives of some of the pioneers of the quantitative analysis of mantle convection as a driving force of вЂ?continental drift’ namely Arthur Holmes, Anton Hales, and Chaim Pekeris, and then two leading proponents of convection and its association with the modern theory of seafloor spreading, subduction, and plate tectonics, Harry Hammond Hess and Stanley Keith Runcorn. Apart from hopefully providing an in-depth perspective on the origins of the science of mantle convection, this survey also reveals the rather fascinating historical ties many of these famous characters had with one another; for example that Rayleigh had become a professor in the institution that Rumford established, that Holmes had studied under Rayleigh’s son, and that Chaim Pekeris was intimately involved with the birth of the state of Israel that Rayleigh’s brother-in-law Arthur Balfour helped create. 7.01.2.1 Benjamin Thompson, Count Rumford (1753–1814) Benjamin Thompson is perhaps one of the more colorful and complex characters in the history of science (Figure 1). He was simultaneously a brilliant observationalist, an egotistical opportunist, and a dedicated social reformer and champion of the poor. His role as spy against the rebelling American colonies on behalf of the British gives him a dubious role in American (although not European) history in that one of the fathers of thermodynamics also played a role not unlike that of Benedict Arnold. Rumford is primarily known for his work on the theory of heat as motion – leading eventually to the kinetic theory and thermodynamics – and for working to debunk the caloric theory of heat. Histories of convection will often note that Rumford is credited as possibly being the first to observe convection; in fact, the study of the mass transport of heat was a significant part of his overall body of work (Brown, 1967), and he wrote an important article on convection in 1797, although the use of the word вЂ?convection’ was not coined until much later, by Prout in 1834 (see Schubert et al., 2001). Benjamin Thompson was born in Woburn Massachusetts in 1753 to a line of Thompsons that can be traced back to a James Thompson who arrived 10 years after the landing of the Mayflower (1620), along with eventual Massachusetts Governor John Winthrop. Thompson’s father and grandfather were reasonably wealthy farmers, but his father died young when Benjamin was less than 2 years old. The family farm was inherited by Benjamin’s uncle who appears to have treated his nephew well with a significant income, a portion of land, and a high-quality education. As with all the subjects of our histories here, Thompson was a brilliant student, displaying talents in mechanics and natural philosophy; however, he was also known for being a somewhat spoiled child at his family’s farm. Thompson left school at age 13 for an apprenticeship in retail, but continued his studies independently in engineering, mathematics, medicine, experimental philosophy, along with French, fencing, music, and draftsmanship. He also carried out independent experiments in science, including astronomy, engineering, anatomy, and nearly electrocuted himself trying to repeat Benjamin Franklin’s experiments on thunderstorm electrification. At age 18, Thompson set out to generate much-needed income and turned to tutoring the children of local wealthy families, which led to his being invited by the Reverend Timothy Walker of Concord, New Hampshire, to run a school in his village. Concord was originally known as Rumford and it is from this town that Thompson was to derive his name upon being ennobled. Thompson courted The Reverend Walker’s daughter, Sarah, who had earlier married a much older wealthy landowner who died after one year of marriage. Less than a year after Sarah was widowed, Thompson married her in 1772 when he was 19. Thompson’s new wealthy wife facilitated his connections with the British governing class, in particular by dressing him up in a fine hussar uniform and parading him about Boston, where he made such an impression on Governor John Wentworth that he was given a British major’s commission in the 2nd New Hampshire Regiment. In 1774, Thompson and his wife had a daughter – also Sarah. By this time hostilities between the Colonies and the Crown had been mounting; these included the Stamp Act and subsequent riots (1765), the Boston Massacre (1770), and the Boston Tea Party (1773), which was followed by both the relocation of the Massachusetts capital from Boston to Salem and the passing of a series of acts, called, by the colonists, the Coercive or Intolerable Acts. These events had by now led to the First Continental Congress in Philadelphia in September 1774, which demanded repeal of these acts, as well as calling on civil disobedience and the buildup of local militia called the Minutemen. Eventually war broke out near Boston in April 1775, at Lexington and Concord. Benjamin Thompson’s acceptance of a British commission in the 2nd New Hampshire Regiment was thus problematic for several reasons. While British officers resented the presence among their ranks of an inexperienced schoolmaster, the people of Concord and Woburn regarded him as a traitor and he had to face two significant challenges: his loyalty to Britain and his new wife’s family ties to the American revolutionaries. Ключевые слова: e, r, o