Ebb and Flow
Tides: A Scientific History. David E. Cartwright. xii + 292 pp. Cambridge University Press, 1999. $74.95.
When in 1687 Edmond Halley presented a copy of Newton's Principia to King James II, he also provided the monarch with a discourse on "the true theory of the Tides, extracted from that admired" book—a discourse that was promptly published. Halley singled out the topic not simply because it illustrated the manner in which gravity accounts for all phenomena of nature—nor even necessarily because it could be expected to appeal to the King given his previous experience with the navy—but, most importantly, because Newton had gloriously succeeded where both Galileo and Descartes had failed. We now know that Halley's enthusiasm was premature, and that old and most persistent problem would not easily yield, so much so that a century later Laplace still considered tidal dynamics as "the spiniest problem" of celestial mechanics. Indeed, not until the late 20th century, following advances in space geodesy and the possibilities opened by powerful computers, did the last vestiges of this intricate global phenomenon give way.
David Cartwright, one of the most distinguished investigators of tidal science, carves for himself a special niche as the first scholar to attempt a comprehensive account of the multifaceted efforts over the past four centuries to solve the mystery of this deceptively familiar natural occurrence. His account, however, is not simply a history of tidal theories. Rather it is an evaluation, arranged in a more or less chronological order, of the scientific content of the publications by the more important contributors to the field. The "minutiae" of historical detail, Cartwright states with a tinge of gratuitous condescension, is relegated to the professional historian, both because in the absence of any secondary literature (save for a few papers on the early modern period) he faced the need to invent the field and because his own "specialist understanding of the subject from many years' personal experience" enabled him to offer an expert panorama beyond the capacities of the run-of-the-mill historian.
Following a brief survey of the gist of the various theories put forward by William Gilbert, Sir Francis Bacon, Galileo, Descartes, and John Wallis during the era of the scientific revolution, Cartwright summarizes the significant contribution of Newton—along with the refinements made to it by Daniel Bernoulli, Leonard Euler and Colin Maclaurin in response to the 1738 essay prize announced by the Académie Royale des Sciences. He proceeds by drawing attention to the importance of the tradition of observations and measurements of tides that was undertaken by members of the early Royal Society and later by French savants. With Laplace's innovative global perspective came the next breakthrough in tidal theory, and, following the introduction of harmonic tidal analysis through the work of William Thomson and George Darwin, it seemed—given the possibility of reliable predictions—as if little remained to be done. Consequently, the initiative for further research passed on to practitioners in the new field of geophysics and oceanography, who, although few, turned their attention to a variety of specialized topics that continued to energize the field. And the second half of the book is devoted to a detailed account of the progress that was made to the discipline by such individuals over the past 75 years.
Cartwright's Tides is a labor of love, based on wide readings and sound judgment, and it is bound to remain the standard reference work on the subject for a long time.—Mordechai Feingold, Center for Science and Technology Studies, Virginia Polytechnic Institute