Abstract
Clarence Edward Dutton (1841–1912) was one of several scientists who laid the foundations for modern geology from their work in North America during the late nineteenth century. Dutton was a career soldier who fought in the American Civil War and remained with the US Army Ordnance Corps to his retirement in 1901. Despite military obligations, Dutton developed a profound interest in geology and, on secondment first to the Powell Survey and later to the fledgling US Geological Survey, made important contributions to volcanic geology, seismology and physical geology. His lifelong fascination with volcanism led to improved understanding of the volcanic geology of the American West, Hawaii, and Central America. This work linked naturally with the emerging science of seismology, as reflected in his study of the 1886 earthquake in Charleston, South Carolina, and he is often credited with introducing the ‘new seismology’ to American scientific audiences. Awareness of volcanic and seismic hazards in turn led him to caution against a proposed sea-level canal across the Nicaraguan isthmus. His contributions to physical geology are most evident in several reports on the American West, notably the Report on the Geology of the High Plateaus of Utah (1880), the Tertiary History of the Grand Cañon District (1882), and Mount Taylor and the Zuni Plateau (1885). These reports, presented in colourful prose, reveal both the author's scientific acumen and his aesthetic appreciation of nature.
Whereas most of Dutton's work must now be placed in its historical context, in his recognition of isostasy, a term he coined in 1882 to reflect the debate then raging concerning Earth's crustal behaviour, his ideas were remarkably prescient. Dutton's interest in isostasy derived in part from his studies of volcanic geology, seismology, and crustal behaviour, and in part from his fieldwork in the American West. Initially, however, it was Dutton's description of the great denudation of the Colorado Plateau, rather than any isostatic implications, that influenced geomorphology during the earlier twentienth century, dominated as it was by Davis' cycle of erosion. The subsequent demise of Davisian geomorphology, and the ensuing quest for alternative models, led to a reawakening of interest in isostasy as a concept basic to the explanation of Earth's surface features. Somewhat belatedly, Dutton's concept of isostasy is once again at the centre of debate regarding denudation and crustal behaviour. Wherever these debates focus, they confront a problem fundamental to geology, geodesy and geophysics, namely the extent to which the Earth's present relief reflects a quest for balance between the subsurface forces generating uplift, subsidence and mass transfers at depth, and the climate-induced processes responsible for denudation and mass transfers of rock waste across the surface. Dutton's probing of isostasy predated modern debate in geomorphology by more than a century.
The establishment of the United States Geological Survey in 1879 brought together some remarkable scientists who had already made significant contributions to geology as members of various independent surveys in the American West. Notable among these were John Wesley Powell (1834–1902), Grove Karl Gilbert (1843–1918), and Clarence Edward Dutton (1841–1912), close friends with differing personalities and talents who combined to advance science along several fronts. The flamboyant Powell, whose reputation had been established from his first exploration of the Colorado River in 1869, occupied the uneasy interface between scientific investigation and sponsoring agencies. The more ascetic Gilbert, the consummate intellectual, grappled with relationships between form and process. The reserved but generous Dutton, the career soldier who addressed scientific questions with great literary skill, complemented the others in several areas and in one respect, his interest in isostasy, was notably farsighted.
Of this trio, Dutton is perhaps the least known, the focus of less attention during his lifetime than Powell, the subject of fewer retrospective accolades than Gilbert. And yet, for a part-time scientist whose most original work was condensed into just 15 years, Dutton travelled widely and achieved much that is worthy of analysis in the light of modern advances in the Earth sciences. This paper outlines Dutton's life and accomplishments, and then reviews his contributions to volcanic geology and seismology, before examining in greater depth his understanding of isostasy and the legacy of this work to later developments in physical geology.
Biographical sketch
Compared with many of his contemporaries, much less is known about Dutton's early and later life because most of his papers disappeared shortly after his death. In contrast, his productive middle years are well represented by his many writings and by records maintained by the various agencies for which he worked. Additionally, many salient facts and perspectives are recorded in obituaries and memoirs, in genealogies of the Dutton family, in later biographies, and in extant correspondence, most notably that with Archibald Geikie during the 1880s.
Clarence Edward Dutton was born on 15 May 1841 in Wallingford, Connecticut, the fourth of five children from the marriage in 1833 of Samuel Dutton (1806–1851), shoemaker and sometime postmaster, and Emily Curtis (1805–1875).1 The Duttons, an extended family with roots traceable to twelfth century England, derived from immigrants to New England during the seventeenth century. Clarence Dutton graduated from Yale College in 1860 where he won a literary prize and established credentials as a mathematician and raconteur.2 The influence of Macaulay's essays and Thackeray's novels was to resurface in his later writings. His strong physique and athletic prowess, notably in gymnastics and rowing, were to serve him well later in the field (Longwell 1958). He then spent a brief period at Yale's theology school but soon felt unsuited to the ministry.
Following the outbreak of the American Civil War in April 1861, Dutton joined the 21st Connecticut Volunteers in September 1862, fighting for the Union cause, as first lieutenant and adjutant. He was wounded at the battle of Fredericksburg in December 1862 and was promoted to captain in March 1863 (Wilson & Fiske 1887–1889). In January 1864, he transferred by examination into the regular army as a second lieutenant in the Ordnance Corps. He was subsequently engaged in conflicts at Cold Harbor, Drury's Bluff, and the Bermuda Hundred before ending the war in command of the ordnance depot of the Army of the Potomac. His elder brother, Arthur Henry Dutton (1838–1864), an engineering graduate from the military academy at West Point in 1861, rose to colonel in the 21st Connecticut Volunteers but was mortally wounded in skirmishing in the Bermuda Hundred and died on 2 July 1864. Meanwhile, Clarence Dutton married Emeline Babcock (born 1840) of New Haven, Connecticut, in April 1864, and they had two children, Marion in 1865 and Clarence Edward in 1871.
The war's end in 1865 saw Dutton posted to the Watervliet Arsenal in West Troy, New York, and he was promoted to first lieutenant in 1867. While there, he was influenced by Robert Whitfield and James Hall, who directed his attention to geology, and by Alexander Holley of the nearby Bessemer Steel Works who interested him in steel production (Diller 1911, 1913; Becker 1912).3 His first scientific paper, On the Chemistry of the Bessemer Process, was read before the American Association for the Advancement of Science at their Troy meeting in 1870. He was posted to the Frankford Arsenal in Philadelphia the same year and then to the Washington Arsenal in 1871, where he remained until May 1876. Promoted to captain in June 1873, Dutton spent the remainder of his career, nominally at least, with the Ordnance Corps, from which he retired in 1901 (Fig. 1).
Captain Clarence Edward Dutton, Corps of Ordnance, US Army.
Dutton's transfer to Washington in 1871 was fortunate. In the aftermath of war, the capital was a hive of scientific, cultural and political activity while the distant surveys of the American West were in full flow under sometimes contentious leadership and variable funding. Dutton soon became engaged in the scientific activities of the capital, notably with the Philosophical Society of Washington. Early critiques of crustal deformation in 18714 and the contraction hypothesis in 18735 showed that he was already pondering some of the more contentious geological issues of his day. His enthusiasm was noted and on 15 May 1875, following recommendations from John Wesley Powell and Joseph Henry, Secretary of the Smithsonian Institution, the War Department assigned Dutton for duty with the Powell Survey. Thus began Dutton's 15-year association with the American West during perhaps the most formative period in North American geology.
Although the American West had been explored to some extent earlier, notably during the railroad surveys of the 1850s, the years immediately following the Civil War saw renewed interest in the region which focused on several major expeditions. The first of these, the United States Geological and Geographical Survey of the 40th Parallel (1867–73) under the direction of noted geologist and mining engineer Clarence King (1842–1901), was designed to render geological maps of the country about to be opened up by the Union Pacific and Central Pacific Railroads.6 The other significant expeditions were the United States Geographical Survey West of the One Hundredth Meridian under Lt. George Montague Wheeler of the War Department (informally called the Wheeler Survey, 1867–79), the United States Geographical and Geological Survey of the Rocky Mountain Region under John Wesley Powell (the Powell Survey, 1867–79), and the United States Geological and Geographical Survey of the Territories under Ferdinand Vandiveer Hayden (the Hayden Survey, 1869–79).
These surveys were undoubtedly aided by completion of the first transcontinental railway in May 1869, but beyond the railheads in northern Utah Territory travel was challenging and accomplished mostly by saddle horse and wagon across difficult uncharted terrain. High elevations, deep canyons, and a continental climate limited most fieldwork to the summer months and even then hazards were posed by thunderstorms and flash floods. By modern standards, these were reconnaissance surveys that focused primarily on topographic mapping and resource identification. Nevertheless they generated some remarkable scientific work, including that arising from the fortunate collaboration of Powell, Gilbert and Dutton. Powell's explorations of the Colorado River in 1869 and 1871–72 had enthralled a larger American audience, whereas Gilbert, who had served with the Wheeler Survey from 1871 to 1874 before joining the Powell Survey, was acquiring a reputation for discerning science.
After helping Gilbert with the intrusive rocks in the Henry Mountains of Utah (Dutton 1877), Dutton progressed from 1875 to 1877 onto Utah's high plateaus where his survey team provided base topographic maps on which Dutton recorded the essential geology. His Report on the Geology of the High Plateaus of Utah appeared in 1880 (Dutton 1880b). He then devoted three field seasons, 1878–1880, to a geological reconnaissance of the Grand Canyon region to the south. When not in Washington, his winters were spent in the west as chief ordnance officer for the Department of the Platte which allowed him time for reflection and writing. He was also one of the co-founders of the Cosmos Club in 1878, a focus for the intellectual elite in Washington.
Meanwhile, competition for responsibilities and resources between the remaining surveys had been resolved in March 1879, after much political wrangling, by the formation of a single United States Geological Survey (USGS), with Clarence King taking office as its first Director on 24 May (King 1880, p. 3). The three surveys were formally discontinued by the US Congress on 30 June 1879, with the USGS, now charged with coordinated surveys of the west, inheriting many of their personnel and much of their scientific work. King was highly regarded but it was Powell, now briefly Director of the Bureau of Ethnography, who was instrumental in encouraging this arrangement and who succeeded King as Director on 19 March 1881 (Powell 1882, pp. xi–xvi). Dutton became head of the short-lived Division of the Colorado (1879–81), one of four regional divisions of the USGS,7 to complete his work in the region. His remarkable study of The Tertiary History of the Grand Cañon District appeared in the Second Annual Report of the USGS for 1880–81 and then in the Survey's monograph series in 1882 (Dutton 1882a). Initially, the work of the USGS was confined to the west but, in August 1882, Congress was persuaded to extend and fund operations nationwide ‘to continue the preparation of a geological map of the United States.’8
At Powell's request, Dutton's scientific work now refocused on volcanic geology, although he had never seen an active volcano. Powell thus made provision for him to visit the Hawaiian Islands in 1882 while Dutton's new assistant, Joseph Silas Diller (1850–1928), began reconnaissance work in the far west (Dutton 1884). Between 1883 and 1886, Dutton's team focused mainly on the volcanic terranes of the Cascade Range, on the then little known volcanoes extending from Lassen's Peak, California, northwards into Oregon and Washington Territory. In 1884, Dutton was formally given charge of the new Division of Volcanic Geology, and was elected to the National Academy of Sciences. During 1883 and 1884, he also studied extinct volcanic terranes in New Mexico Territory, access to which had been aided by completion of the second transcontinental railway in March 1881. This work appeared as Mount Taylor and the Zuñi Plateau in the Sixth Annual Report of the USGS in 1885 (Dutton 1885a).
On 31 August 1886, while Dutton was working in the Cascade Range in Oregon, a major earthquake occurred in the Charleston area of South Carolina. Dutton was invited by Powell to study the event and, reaching Charleston in October, began a thorough investigation that was to culminate in his report of 1889 (Dutton 1889a). The latter year also saw Dutton address the Philosophical Society of Washington On Some of the Greater Problems of Physical Geology, a paper in which he formally introduced the word ‘isostasy’ although he had in fact used it earlier.
However, Dutton's involvement with the American West was changing. In the Tenth Annual Report to the US Congress for 1888–89, Director Powell had noted that the duties of the USGS now extended to ‘the investigation of the extent to which the arid regions of the United States can be redeemed by irrigation …’ (Powell 1890, p. 3). Ever willing, on 1 July 1888 Dutton became head of the hydraulic branch of the new Irrigation Survey where he initiated studies of precipitation, evaporation, stream flow and suspended sediment discharge, and evaluated the potential for engineering works such as dams and canals (Dutton 1890).9 However, despite Dutton's warnings, Powell continued to use some irrigation survey funds to support general topographic mapping. This brought rebuke from Congress, irrigation being a sensitive issue in Washington, and in his Twelfth Annual Report for 1890–91 Powell noted that ‘a portion of the work of the Irrigation Survey was discontinued’ (Powell 1891, p. 5). Dutton may have been a casualty of these events. After his report on irrigation for the 1888–89 fiscal year (Dutton 1890, p. 78–108), he made no further contributions to USGS publications.
Although Dutton may have left the USGS at his own request following the disagreement with Powell, he was evidently not happy at this turn of events. In a letter of 6 June 1891 to Archibald Geikie (1835–1924), Director General of the Geological Survey of Great Britain, Dutton said that he was again fully employed by the War Department, having been promoted to major on 1 May 1890, but expressed dismay at being transferred from Washington, D.C., to the San Antonio Arsenal, Texas, where he saw no life for himself.10 Somewhat sadly, he told Geikie that he was considering writing a cowboy novel or possibly a historical novel about Davy Crockett.
Whether or not these novels were ever written, Dutton found new life, during furloughs from Texas, by visiting volcanoes in Mexico and Central America, and by preparing reports on the proposed inter-ocean canal through Nicaragua for the US Congress in 1892 (Dutton 1891–1892). In 1899, he was recalled to duty in the office of the Chief of Ordnance in Washington, D.C., but on 7 February 1901, at his own request, he retired from active service (Pyne 1999, pp. 172–173). His book on Earthquakes in the Light of the New Seismology appeared in 1904 (Dutton 1904), and in his last major paper, in 1906, he returned to explain volcanoes in relation to the recently discovered concept of radioactivity (Dutton 1906).11 After several years of declining health, he died from arteriosclerosis at his son's home in Englewood, New Jersey, on 4 January 1912. He apparently just fell asleep. Among his last words were ‘Farewell to my old friends on the Geological Survey’ (Diller 1913, p. 16).12
Volcanic geology
Dutton's interest in volcanic geology, reflecting perhaps his early exposure to molten ores in Troy's furnaces, was stimulated by contemporary theoretical debates regarding Earth's crustal behaviour and then by familiarity with the Tertiary lavas that spewed onto the Colorado Plateau. His first field season in charge of the Division of the Colorado in 1879 had focused on the topographic survey (by John Renshawe) and geological mapping of the arid Uinkaret Plateau where perhaps 200 volcanic vents and basaltic flows, dominated by Mount Trumbull (2447 m), cover Carboniferous and Permian sedimentary rocks above the North Rim of the Grand Canyon (Dutton 1880a, pp. 29–31). Several of these cones are perched on the brink of the canyon and spill coulées of olivine basalt into the gorge and nearby valleys such as the Toroweap. To illustrate these relationships, his 1882 report on the Tertiary History of the Grand Cañon District included drawings of Mount Trumbull, of dykes in the canyon wall, and of recent lava flows on the Uinkaret by artist-geologist William Henry Holmes (1846–1933), and of lava falls in the inner gorge by romantic artist Thomas Moran (1837–1926) (Dutton 1882a, Plates XVIII–XXI). Distinguishing between the older basalt flows on the plateau and younger basalts cascading into the gorges, he inferred a relatively recent age for the incision of the Grand Canyon. In the following field season, 1880, he asked Richard Goode to complete a topographic survey of the comparable extinct volcanic field in the San Francisco Mountains just south of the Grand Canyon (Dutton 1882b, note 13, pp. 5–10).
Thus, when Powell asked him to direct his attentions towards volcanic geology in 1882, Dutton was no neophyte. But neither had he seen an active volcano. Indeed, his limited experience showed in a letter to Archibald Geikie in January 1881, wherein he recognized only two categories of volcanic eruption: what he termed, from the literature, the Mediterranean-type of frequent small events and cinder cones, and from his own field studies, the Rocky Mountain-type of fewer but larger eruptions over a wide area.13 Powell therefore provided funds for Dutton to visit the Sandwich (Hawaiian) Islands from May to October 1882.
Dutton was by no means the first geologist to examine the Hawaiian volcanoes. For example, James Dwight Dana (1813–1895), later Professor of Natural History and Geology at Yale, had visited them between 1838 and 1843 (Dana 1849). Dutton spent much of his time on the big island of Hawaii, observing the active caldera at Kilauea, the legacy of fissure and crater eruptions from the frequently active pile of Mauna Loa, the olivine-rich lava flows, the dormant Hualalai, and the dissected features of extinct Mauna Kea and Kohala. He concluded that the lavas of Kilauea were generated in shallow reservoirs only 1–4 km beneath the surface. He also made briefer excursions to Maui, Kauai, Molokai and Oahu, recognizing as had others before him that volcanic activity ceased earlier as one progressed NW from Hawaii, although he erred in saying that this did not necessarily mean that the eruptions to the NW began earlier.14 In a letter written to Dana after his return, Dutton admitted that he had made no great discoveries but that:
I understand much better than I ever did before the action and behavior of lavas, their modes of accumulation and their methods of flowing.15
No doubt invigorated by his sojourn in the Hawaiian Islands, Dutton prepared to apply his new knowledge to the Cascade Range in the far west. The problem was that, although Gilbert Thompson and M.B. Kerr had begun topographic surveys there in 1882 and 1883, ‘in 1884 the topographic survey and mapping of that country had not sufficiently progressed to enable systematic geological work to proceed satisfactorily.’ (Dutton 1885a, p. 114). He also found the maps of the earlier Wheeler Survey ‘wholly unsuited for geological work.’ (Dutton 1888, p. 97). He therefore took the opportunity to examine part of New Mexico territory, where topographic mapping had begun under J. Howard Gore and Gilbert Thompson as early as 1881. In his subsequent report on Mount Taylor and the Zuni Plateau he focuses in part on the great volcanic pile of Mount Taylor. In a letter to Geikie in 1884, he again distinguishes between the thick older flood basalts on the plateau and the more recent lava flows flowing up to 160 km from vents on Mount Taylor.16
Thus, after significant delays, studies of the volcanic geology of the Cascade Range began in earnest in 1885. Dutton's new assistant, Joseph Silas Diller, had begun reconnaissance work from Mount Shasta to the Columbia River in 1883 and 1884, collecting samples for petrographic analysis and observing the relationship between the volcanic and other rocks of the region. It was not until 1885 that Dutton, now head of the Division of Volcanic Geology, began serious field studies there. His 1885 field season focused mainly on northern California, on the vast volcanic pile of Mount Shasta (4317 m), isolated from the main Cascade Range, and on Lassen's Peak (3187 m) and the Modoc volcanic plateau (Dutton 1888, pp. 99–100). He recognized the mostly andesitic and basaltic nature of the lavas, while the superposition of recent lavas on Cretaceous and early Cenozoic sedimentary rocks allowed him to establish a maximum age for later volcanism. Later in 1885 and in 1886, he followed the range northward through Oregon to the Columbia River.
During 1886, he undertook a study of Crater Lake, a mid-Holocene caldera in the Cascade Range (Dutton 1888, pp. 97–103). This involved the construction of three boats in Portland, their transport by rail to Ashland, and thence by wagon to the lip of the caldera's near-vertical walls down which they were lowered by an infantry detachment (Dutton 1888, pp. 102–103). Some 168 soundings of the lake were obtained by lowering a piece of pipe on a spool of piano wire from the stern of the Cleetwood, the half-ton survey boat. The maximum recorded water depth of 608 m was remarkably close to the sonar depth of 589 m obtained in 1959.
He also attempted to understand the complex geology of the Coast Ranges of northern California and Oregon which he thought were in some way related to Cascade volcanism. He stated:
The terms dip and strike here lose all significance, for everything like system or order in the arrangement of the beds (or of what once may have been beds) has been obliterated by crushing or crumpling forces which have acted upon them. The folding and distortion have not resulted here in a systematic plication like that of the Appalachians, as if by a force acting in a single or two opposite directions, but by forces from every possible direction. (Dutton 1888, p. 100)
Today, several generations later, geologists armed with an understanding of accretionary and subduction tectonics continue to struggle with the issues posed by these ranges.
Further studies in volcanic geology were interrupted by the Charleston Earthquake of August 1886, the report on which precluded fieldwork during the 1887–88 fiscal year, and by his subsequent involvement in the fledgling Irrigation Survey from July 1888. He retained an interest after leaving the USGS, however, and was able to visit volcanoes in Mexico and Central America while on furlough from the San Antonio Arsenal.
In his oft-quoted 1889 paper, Dutton recognized three important questions in physical geology, the first of which was: ‘What is the potential cause of volcanic action?’ (Dutton 1889b). He considered the problem then unsolved and thus declined to answer. Later, in his last paper in 1906, following the discovery of radioactivity in 1896,17 he returned to the theme. Here he states that volcanic eruptions ‘are caused … by a development of heat, resulting from radioactivity, in limited tracts at a depth of one to three—at the very utmost not over four—miles from the surface …’ He supported this argument from his belief in shallow reservoirs beneath Hawaiian volcanoes and from recent measurement by others of radioactivity in soils, rocks and hot springs. In seeking to lay to rest, one more time, the contraction hypothesis of Earth's history, he emphasized that the heat generated by radioactivity far exceeded that lost to the atmosphere and space through conduction and radiation. The 1906 paper was an excerpt from a book on volcanism that he was preparing but never published. In a letter shortly before his death, Dutton reaffirmed his interest in volcanicity but considered its cause still unresolved.
Seismology
Dutton's interest in seismology was probably kindled by his broader concern for questions of Earth's crustal stability and by his exposure, while in the Hawaiian Islands, to minor earthquakes associated with volcanic eruptions. Also, his report for the 1884–85 fiscal year was remarkably prescient in noting that several earthquake tremors had occurred during 1884 along the Atlantic seaboard of the United States. Dutton convened a group that included representatives of the US Naval Observatory and the Signal Service, and also William Morris Davis (1850–1934) of Harvard, to investigate the practicality of setting up an earthquake observation network (Dutton 1885b, p. 61). Lacking suitable instruments, they concluded that this was not feasible and that it was best to rely on a network of voluntary observers during and after specific earthquake events.
Dutton was on the Warm Spring Indian Reservation east of the Cascade Range when the Charleston Earthquake occurred on 31 August 1886 (Dutton 1889a, p. 209). He learned of this event, and of Powell's request that he undertake its investigation, on reaching Portland on 10 September. Dutton's understandably delayed arrival in Charleston in mid-October was hardly ideal but, fortunately, W. J. McGee (1853–1912) of the USGS and Thomas Corwin Mendenhall (1841–1924), then of the US Signal Service, had been dispatched to the scene immediately after the earthquake. With additional input from local observers Earle Sloane, G. E. Manigault, Carl McKinley and others, and with questionnaires circulated by Ensign Everett Hayden of the US Navy, Dutton was able to assemble unusually detailed facts regarding the timing, propagation and intensity of the earthquake.
One feature that makes the Charleston event particularly noteworthy is that this was the first strong earthquake to occur in the United States following the adoption of standardized clock time and time zones throughout the nation in 1883. There had of course been earlier historic earthquakes, notably in the central Mississippi Valley and California, but the Charleston event was the first substantial event whose effects could be timed over a large area. Hindcasting from available data suggests that the Charleston earthquake had a moment magnitude (M) of 7.3, the largest such event in the eastern United States in historic time (Johnston 1996).
Dutton's report on the Charleston earthquake is a remarkably fine document, considering the facilities and understanding of the time. Refining Robert Mallet's approach to the Neapolitan earthquake of 1857, Dutton developed a new isoseismal method for estimating the depth of the earthquake focus by identifying two critical points, the epicentrum and a point on a radius from the epicentrum at which shock intensities diminished most rapidly, which in turn allowed him to define an index circle of comparable points around the epicentrum. He identified two foci, one at a depth of about 20 km beneath Woodstock, the other at a depth of about 13 km beneath Rantowles (Fig. 2). Regarding the event's wider impact, he plotted questionnaire and interview data on the recently developed Rossi-Forel scale of earthquake intensity. The resulting isoseismal map showed that the event was felt as far north as New England and southern Ontario, and westward into the Mississippi valley (Fig. 3). He also improved understanding of the propagation velocity of earthquakes, which for the Charleston event he determined to be 5184 m s−1. He was thus able to devote much attention to the nature and mechanisms of earthquake wave motion but, lacking information, he refrained from speculating on the cause of this event.
The Charleston earthquake of 1886; isoseismals within the epicentral tracts (Dutton 1889a).
The Charleston earthquake of 1886; isoseismals throughout eastern North America (Dutton 1889a).
Although he never investigated another major earthquake, in retirement Dutton presented his knowledge in a book on Earthquakes in the Light of the New Seismology, published in 1904 (Dutton 1904). This book of 16 chapters defines two classes of earthquake (volcanic and tectonic), analyses seismic vibrations, propagation rates and wave forms, discusses relevant aspects of the Earth's crustal properties, and seeks to explain the distribution of earthquakes across the globe. He also returned, in his 1906 paper on volcanoes and radioactivity, to defend his isoseismal method for defining earthquake depth and thereby intensity, but by then the field had moved on.
Crustal behaviour, isostasy and denudation
Generations of Earth-science texts indicate that the term isostasy was first coined by Dutton in his 1889 address On some of the greater problems in physical geology but in fact he had introduced the term in 1882 in a review of Physics of the Earth's Crust by the Reverend Osmond Fisher (1817–1914) (Fisher 1881). Fisher, for many years rector of Harlton, Cambridgeshire, was a leading opponent of the then prevailing contractional hypothesis of mountain building, a view in which he found a ready ally in Dutton. In a footnote to the 1882 review, Dutton stated that:
In an unpublished paper I have used the terms isostatic and isostacy to express that condition of the terrestrial surface which would follow from the flotation of the crust upon a liquid or highly plastic substratum;—different portions of the crust being of unequal density (Dutton 1882c).
The ‘unpublished paper’ to which Dutton referred was presumably to become his 1889 address to the Philosophical Society of Washington, not published until 1892, in which he formally proposed the term isostasy (having, on the advice of Greek scholars, changed the ‘c’ to an ‘s’).
There were essentially three series of events that brought Dutton to this stage: first, the debate then raging among geologists concerning the Earth's crustal behaviour; second, Dutton's own theoretical musings derived from the literature and discussions with other scientists; and third, his field observations on the Colorado Plateau.
The debate concerning the Earth's crustal equilibrium already had a lengthy heritage in Dutton's time. Leonardo da Vinci (1452–1519) had speculated on it around 1500 (Delaney 1940).18 Then, in a critical period from the mid-eighteenth to the mid-nineteenth centuries, a succession of European surveyors, mathematicians and astronomers became intimately involved in vexing questions regarding Earth's shape and the origins of mountains. Among these, Pierre Bouguer (1698–1758) recognized gravity anomalies in the Andes which R. G. Boscovich (1711–1787) attributed to thermal expansion of rocks at depth that generated surface uplift and subsurface voids.19 More directly relevant to Dutton's ideas were those expressed by John Herschel (1792–1871) in the 1830s. Herschel, in a letter to Charles Lyell included in a treatise by Charles Babbage (1792–1871) (Herschel 1837), expressed his belief that sediment loading at ocean margins caused sea-floor subsidence and consequent uplift of continental margins. It is unfortunate that Herschel illustrated this hypothesis from the emergent shorelines of Scandinavia but in other respects it was an interesting notion. Shortly afterwards, the Survey of India, directed by George Everest (1790–1866), found discrepancies between the geodetic and astronomic positions of locations on the Ganges Plain, which he attributed to geodetic errors of closure. John Henry Pratt (1809–1871), then Archdeacon of Calcutta, disagreed. In a paper read to the Royal Society in 1854, Pratt suggested that the discrepancy was due to the gravitational effect of the Himalayas but he computed that such an effect was likely to be more than three times the observed value (Pratt 1855). George Biddell Airy (1801–1892), the Astronomer Royal, was not surprised at the discrepancy and reasoned from simple principles that Earth's outer layers comprised a thin crust overlying a denser fluid layer of ‘lava.’ (Airy 1855). He likened this relationship to timber rafts of comparable density but differing heights floating on water, the taller blocks supported by timber reaching greater depths beneath the water. In further papers, Pratt responded with his own theory by implying that elevated regions were underlain by low density rocks whereas depressed regions were underlain by high density rocks (Pratt 1864). The Pratt and Airy hypotheses were of course germane to the other contentious issue of the time, namely the origin of mountain ranges which, with some notable exceptions, most scientists of the day, including Pratt, attributed to the Earth's progressive cooling and periodic contraction through time.
All these observations and hypotheses were grist to Dutton's mill. Not yet 30 years old, he entered this debate with vigour with an address to the American Philosophical Society in Philadelphia on 7 April 1871 (Dutton 1873, pp. 70–72).20 In this paper, published in 1873, Dutton explained regional crustal deformation in terms of changes in rock density following metamorphism. He hypothesized that uplift was caused by the expansion of rocks whose density had been lowered by water added during metamorphism. Subsidence was caused by rock contraction which reduced volume but increased density. Volcanism occurred as shallow crustal rocks became lighter when super-saturated with water and were displaced upwards through vents and fissures by subsiding heavier overlying rocks. He believed that volcanism would thus coincide with elevated regions, invoking as evidence the Rocky Mountains which had experienced scattered Miocene and Pliocene volcanism.
Dutton expanded his thesis in two subsequent papers to oppose the then prevalent contraction hypothesis of mountain building. In 1874, based on Fourier's cooling theory and Thomson's calculations, he argued that there had been little cooling of Earth's nucleus over time and therefore that contraction due to secular cooling could not explain the formation of mountain ranges, certainly not those of post-Cretaceous age (Dutton 1874).21 In 1876, he observed that the mechanical force ‘arising from contraction by cooling is many times less than the quantity required for mountain building’ (Dutton 1876). He also felt that both the varying ages, dimensions and distributions of mountain ranges were inconsistent with uniform and progressive contraction of Earth's nucleus. However, he offered no theory to replace the contraction hypothesis.
By 1876, Dutton was aware of similar views held by Osmond Fisher and when Fisher's Physics of the Earth's Crust appeared in 1881, Dutton used his complimentary review as a forum to promote his own ideas. In his book, Fisher sought to destroy the contraction hypothesis which Dutton called ‘nothing but a delusion and a snare, and that the quicker it is thrown aside and abandoned, the better it will be for geological science’ (Dutton 1882c, p. 287). Instead, Fisher assumed a rigid crust overlying a liquid or plastic substratum on which the crust is in approximate hydrostatic equilibrium.
The crust must be in a condition of approximate hydrostatical equilibrium, such that any considerable addition of load will cause any region to sink, or any considerable amount deduced off an area will cause it to rise. (Fisher 1881, p. 275)
Such flotation allows the crust to shift laterally. Lateral compression in turn produces narrow fold belts and crustal thickening, nine-tenths of which lie below the mean surface of the crust. Fisher was at a loss to explain lateral compression of this magnitude but inclined to invoke elastic vapours and fissures in the lower crust. This allowed Dutton in his review to explore an alternative explanation for mountain building, namely isostasy.
Neither Fisher nor Dutton were really comfortable with the reasoning behind isostasy, invoking both the Airy and Pratt hypotheses. Thus, in paraphrasing Fisher's views, Dutton states:
The height to which the surface of the disturbed tract will rise above the mean level will be proportional to the difference of densities of crust and substratum respectively and also to the amount of local thickening of the crust by the compression. The ratio of the density of the crust to the density of substratum he [Fisher] takes at about 0.905, which is not far from that of ice to water. Hence when a disturbed tract of the crust is thickened by compression much the greater part of the thickening consists in additions to the under surface of the crust and only a small part in additions to the upper surface. The bulge downward is some nine times greater than the bulge upward. (Dutton 1882c, p. 286)
This invocation to the Airy hypothesis is followed by one to the Pratt hypothesis as Dutton prefaces his concept of ‘isostacy’ (sic) by summarizing Fisher's observation of flotation thus:
The profiles of the earth therefore become, in their broader features, simply those which are due to flotation. The higher portions float higher because they are less dense; the depressed portions sink deeper because they are more dense. (Dutton 1882c, p. 289)
Meanwhile, Dutton's field studies of the American West had opened a Pandora's box of evidence to support his rejection of contraction theory and his belief in isostasy. His 1876 paper contains the first reference to the Colorado Plateau, which he had first seen during the 1875 field season, concluding from its elevated horizontal strata that the plateau was obviously not the result of contraction. But in 1885, in his report on Mount Taylor and the Zuni Plateau, he concluded that ‘The mountains of the West have not been produced by horizontal compression, but by the action of some unknown forces beneath which have pushed them up’ (Dutton 1885a, p. 198).
His field studies on the plateau, however, also exposed him to the vast amount of denudation that had been inflicted by the Colorado River and its tributaries (Fig. 4). He was particularly impressed by the evidence for massive uplift of the plateau's more-or-less horizontal rocks, and the vast thickness of Mesozoic and Cenozoic sedimentary rocks that must have been removed by erosion to expose the Palaeozoic strata in and around the canyons. Significantly, in his 1882 monograph on the Tertiary History of the Grand Cañon District, Dutton stated:
The Grand Canyon dissecting the Colorado Plateau, providing evidence of great uplift and great denudation captured by artist-geologist William Henry Holmes in a chromolithograph, 1882 (Dutton 1882a).
If it be true that the Grand Cañon district received between the close of the Carboniferous and the close of the local Eocene 10,000 feet of deposits averaged over its entire surface, it follows that at the latter epoch the summit of the Carboniferous lay at least 10,000 feet below sea-level and was much more nearly horizontal than it is at present. And if such was its position and configuration, the great faults and displacements which traverse it must be of Tertiary age, and there must have been an enormous amount of uplifting, ranging from 12,000 to 18,000 feet, in various portions of the district. These are some of the consequences of the great denudation. (Dutton 1882a, p. 69)
He referred frequently to the great uplift (in the early Cenozoic) and the great denudation (in the late Cenozoic) of the Colorado Plateau (Fig. 5), mostly in the sense that uplift triggers denudation. Only in the above segment does he hint that denudation causes uplift.
The Grand Canyon and Colorado Plateau from Point Sublime, drawn by artist-geologist William Henry Holmes (Dutton 1882a).
Dutton's 1889 address to the Philosophical Society of Washington is a curious document. In identifying three of the greater problems of physical geology, he identifies (1) the cause of volcanic action (which he considers unsolved and therefore ignores); (2) the cause of regional elevation and subsidence (for which he finds no satisfactory explanation); and (3) ‘the cause of the foldings, distortions, and fractures of the strata’ (which he examines) (Dutton 1889b, p. 201).
Returning to earlier arguments concerning mountain building, he rejects the contraction hypothesis for want of an adequate mechanism and as unsuited to the field evidence. He then formally proposes the term isostasy ‘for this condition of equilibrium of figure, to which gravitation tends to reduce a planetary body’ (Dutton 1889b, p. 203) and discusses the great sedimentary bodies of the Appalachian Mountains and the Colorado Plateau which were deposited near sea level and whose great thickness can only be explained by subsidence caused by sedimentation. He then observes that ‘wherever broad mountain platforms occur and have been subjected to great erosion the loss of altitude by degradation is made good by a rise of the platform’ (Dutton 1889b, p. 204). With reference to the western plateaus, he opines that ‘the flanks of these platforms … plainly declare to us that they have been slowly pushed upwards as fast as they were degraded by secular erosion’ (Dutton 1889b, p. 204). In summary, he states that plateau uplift following erosion and subsidence following deposition ‘are, in the main, results of gravitation restoring the isostasy which has been disturbed by denudation on the one hand and by sedimentation on the other’ (Dutton 1889b, p. 204). He invokes Babbage, Herschel and Pratt in support of his thesis. He explains fold systems (plications) as a result of lateral viscous flow from beneath sediment-loaded littoral basins towards the unloaded continent, invoking as evidence the fold belts found inland from both the Atlantic and Pacific coasts of the United States. But he denies that isostasy is responsible for regional elevation and subsidence, which he attributes, as in 1871, to the expansion and contraction of magmas, respectively (Dutton 1889b, p. 211). It is difficult to avoid the conclusion that, with isostasy, Dutton identified and named an interesting concept but applied it to the wrong problem.
Dutton's legacy
Although most of Dutton's work must now be consigned to its historical context, interesting at the time but superseded by later advances, he leaves a legacy that is both literary and scientific.
Literary legacy
Dutton's word pictures of the American West attracted much complimentary interest during his lifetime and have since achieved legendary status. His facility with the English language, influenced early on by Macaulay's essays and Thackeray's novels, was now stimulated by field experiences in the west. His three monographs on the Colorado Plateau are remarkable as much for their colourful prose and aesthetic appreciation of nature as for the striking illustrations of Holmes and Moran. Working in virgin territory, he was not shy at introducing new names for spectacular features. Deeply influenced by eastern culture, he named many features of the Colorado Plateau after Hindu gods, for example Shiva Temple and Vishnu Temple.
Diller, in 1911, paid tribute to Dutton's simple euphonious style and considered him one of the best writers of popular geological science of his day (Diller 1911, p. 137). George Ferdinand Becker's obituary acknowledged Dutton's clarity and simplicity of expression but added, more critically, that ‘Ease of expression, however, may be a dangerous gift and Dutton did not always reason soundly’ (Becker 1912, p. 387). This may have been due to his methods. Diller reported that Dutton rarely made use of field notes, excepting for figures, read much and discussed ideas with colleagues, but did not prepare a written plan or preliminary draft of his written work. As Diller stated: ‘… when ready, he penned all his own manuscripts rapidly under the stimulus of an enthusiasm begotten by a consciousness of his comprehensive and complete knowledge of the subject’ (Diller 1913, pp. 15–16). Understandably, Dutton's imagination sometimes outdistanced the facts.
Dutton's writings and Holmes' drawings did much to stimulate popular interest in the American West. Wallace Stegner (1909–1993), regarded as the dean of western writers during the mid-twentieth century, later observed with respect to the Grand Canyon that ‘though it is Powell's monument to which the tourists walk after dinner to watch the sunset from the South Rim, it is with Dutton's eyes, as often as not, that they see’ (Stegner 1953, pp. 173–174).22
Scientific legacy
Dutton was among the most prominent American scientists of his time, a reserved person of great integrity and charm, who collaborated easily with others and yet emerged as an intellectual force in his own right. To the modern eye, his scientific legacy is undoubtedly shrouded by colourful prose, rambling digressions, and little regard for economy of style, but his search for explanation still shines through. His geology was largely self-taught and he readily acknowledged the debt he owed to his collaboration with Powell and Gilbert, thus:
In daily intercourse with Powell and Gilbert, and with the bond of affection and mutual confidence which made the study in a peculiar sense a labor of love, this geological wonderland [the Colorado Plateau] was the never-ending theme of discussion; all the observations and experiences were common stock, and ideas were interchanged, amplified and developed by mutual criticism and suggestion. The extent of my indebtedness to them I do not know. Neither do they. I only know that it is enormous, and if a full liquidation were demanded it would bring me to bankruptcy (Dutton 1885a, p. 113).
Dutton was also generous in praise of earlier scientists. Thus, although later scholars often identify Dutton with isostasy, which he presented in 1889 ‘in modified form, in a new dress, and in greater detail,’ he clearly credited the theory to Babbage and Herschel (Dutton 1889b, p. 206). He also gracefully extolled the virtues of his field assistants, such as Diller and Hayden, and the many topographic surveyors on the Colorado Plateau.
Among his individual contributions to volcanic geology, he correctly identified the spatial and temporal relationships between Tertiary volcanic features and the dissection of the rising Colorado Plateau. He saw that Hawaiian volcanoes ranged from active through dormant to extinct as he moved northwestward through the islands. He recognized relationships between the Tertiary and Quaternary volcanics of the Cascade Range, earlier country rocks and later dissection. But time and knowledge have passed on and we now know so much more from subsequent developments in plate tectonics relating to Colorado Plateau uplift, Hawaiian volcanism, and the Cascadia subduction zone. For example, his belief that Hawaiian lavas emanated from shallow reservoirs, perhaps 1–4 km deep, was correct only in defining their immediate source. Subsequent studies of earthquakes beneath Kilauea, for example, suggest that the magma originates some 50–80 km beneath the volcano, in the upper mantle some 30–60 km beneath the oceanic crust, and moves upward through a roughly cylindrical conduit to a shallow magma reservoir only 2–5 km deep (Macdonald et al. 1983). Nor did he anticipate the hotspot explanation for sequential Hawaiian volcanism first proposed by Wilson (1963). What Dutton did was to improve the fundamental body of knowledge regarding these features, garnished with sometimes logical, sometimes speculative, observations regarding their origin and significance. In short, like many of his contemporaries, he helped to prepare the way for later scientists by proposing hypotheses that could not be tested at the time.
In similar vein, Dutton's legacy to seismology may be viewed as a way station in a rapidly changing field. Certainly, his 1889 report on the Charleston earthquake of 1886 was in its time a remarkable compilation of facts and theory. This M7.3 event remains enigmatic but a 600-km-long, NNE-trending, east coast fault system beneath the Atlantic Coastal Plain has recently been identified as its probable source (Marple & Talwani 2000). Although this structure affects Cretaceous and Cenozoic sediments, it is not visible at the surface. Thus, with the limited techniques then available, Dutton could neither have inferred such a structure nor its coincidence with the margins of buried Mesozoic rift basins and pre-Mesozoic exotic terranes beneath eastern North America. He did, however, provide a wealth of data as a basis for later work. However, his 1904 book, which some contemporaries viewed as introducing the ‘new seismology’ to American scientific audiences, soon became dated. In his obituary in 1912, George Becker acknowledged that the book showed Dutton at his best but that it was ‘far from exhaustive and cannot be regarded as an adequate presentment of the subject at the time of its publication.’ (Becker 1912, p. 388). But to his credit, Dutton continued to probe the unknown, stating in the book's preface that the volcanic and tectonic causes of earthquakes were ‘apparently quite distinct, though possibly they may have interrelations not yet recognized.’ Shortly before Dutton's death, Diller lauded him as ‘the first seismologist of his country’ (Diller 1911, p. 137) but in his later obituary toned this down to ‘one of the first seismologists of his country’ (Diller 1913, p. 10).
With respect to crustal behaviour, Dutton's ideas began to be superseded during his own lifetime and certainly later by developments in plate tectonics. His early contributions during the 1870s were quite bizarre, showing an imperfect understanding of physical processes and an inadequate knowledge of field situations. He erred, for example, in his understanding of magma and sources of volcanism. Yet his arguments against the contraction hypothesis of mountain building were sound enough, reflecting a rising tide of opposition echoed by many of his contemporaries. His recognition that Earth's great fold belts also involved areas of massive sedimentation and subsequent crustal shortening, perhaps reflecting the ideas of his early mentor, James Hall, also heralded later understanding of orogenic systems. Nevertheless, his writings on these topics appear today as archaic legacies of a bygone age.
His contribution to isostasy was different. He introduced the term, even if he did not fully understand its implications. In doing so, he reflected notions regarding Earth's crustal equilibrium that had floated back and forth for some time, certainly since Babbage and Herschel pondered the subject in the 1830s. But they did not give the process a name; Dutton did and in doing so provided a focus for later work in geodesy, geophysics and geology.
The term isostasy was readily accepted during Dutton's lifetime and within a few years a flurry of scientific activity began to emerge under this rubric. Geodesists such as John Hayford (1868–1925), Chief of the Division of Geodesy of the US Coast and Geodetic Survey, recognized the significance of isostatic equilibrium and adopted the Pratt model, which simplified computation, to correct the triangulation surveys of the United States (Hayford 1909). His successor, William Bowie (1872–1940), also invoked the Pratt hypothesis and published an entire book on isostasy in 1927 (Bowie 1927). Indeed, the Pratt hypothesis often came to be known as the Pratt-Hayford model.
Meanwhile in Europe, John Joly (1857–1933), geophysicist of Trinity College, Dublin, followed Dutton in emphasizing the significance of both radioactivity and isostasy to crustal processes in books on Radioactivity and Geology (Joly 1909) and The Surface History of the Earth (Joly 1925). The latter is essentially a view of Earth's surface from below, ‘based directly upon two great recent advances in our knowledge of the earth's crust’ (Joly 1925, p. 5). In Finland, geodesist W. A. Heiskanen (1895–1971) of Helsinki's Superior Technical School, favoured the Airy model for his isostatic computations, later referred to as the Airy-Heiskanen model (Heiskanen 1931).
In contrast, many geologists of the early twentieth century were reluctant to enthuse over isostatic models that they considered static and based on mathematical massaging of crustal assumptions that could not be proven at the time. A notable exception was Andrew Lawson (1861–1952), Professor of Geology at the University of California, Berkeley, who published on The Geological Implications of the Doctrine of Isostasy in 1924 (Lawson 1924). Lawson described the various ways in which shifts of mass may occur at and beneath the surface, several of which were testable. For these, he invoked both closed-systems, in which isostatic adjustment is achieved by local subcrustal flow from loaded to unloaded regions, and quasi-closed systems in which shifts of load cannot be restored by local compensation and which therefore involve deformation of the geoid.
Lawson's arguments, among others, made little impression on the developing field of geomorphology, dominated as it was by William Morris Davis of Harvard University. It was Dutton's descriptions of the ‘great denudation’ of the Colorado Plateau, rather than any isostatic implications, that captured Davis' attention. Prolonged denudation was the necessary precursor to peneplanation, the end stage in Davis' cycle of erosion. Furthermore, in an ideal cycle, initiated by rapid uplift and followed by lengthy structural quiescence, isostatic adjustments to denudation were an unwelcome complication. Localized isostatic responses to ice loading, as discussed by Reginald Daly (1871–1957) (Daly 1934), could be tolerated but large-scale responses to denudation were better ignored.
The demise of Davisian geomorphology during the middle decades of the twentieth century, and subsequent advances in plate tectonics, led to a reawakening of interest in isostasy as a concept basic to the explanation of Earth's surface relief. Somewhat belatedly, Dutton's concept of isostasy has once again emerged at the centre of debate regarding denudation and crustal behaviour (Molnar & England 1990). Wherever these debates focus, whether on the American West or the Himalayas or the Andes (Gregory-Wodzicki 2000), they confront a problem fundamental to geology, geodesy and geophysics, namely the extent to which Earth's present surface relief reflects a potential balance between subsurface forces generating uplift, subsidence and mass transfers at depth, and the climate-induced processes responsible for denudation, sedimentation and mass transfers of waste across the surface. In recent years, a combination of geodetic and geophysical methods has done much to restore the significance of isostasy to geomorphology.
Conclusion
Dutton's contribution to geology was always going to be superseded, as befits scientific progress, but his quest for explanation, for seeking to understand the bigger picture from a myriad of local details, is a message for all scientists. As he stated:
I am fond of viewing the facts observed in the field in their relation to broader and more general facts, and of marshaling them into their proper places (Dutton 1885a, p. 198).
He was gifted, perceptive, articulate, highly literate and much travelled, willing to take on challenges for which, as a largely self-taught geologist, he was not always prepared. But he learned quickly. He may not always have been correct but he deserves recognition for addressing these larger issues. His ideas relating denudation to isostasy were remarkably prescient and, although largely ignored by geomorphology for almost a hundred years, have re-emerged at the cutting edge of contemporary scientific enquiry.
Acknowledgments
I warmly thank K. B. Bork and R. H. Dott, Jr. for their discerning and helpful reviews of this essay.
Footnotes
↵Dutton family genealogy, 1177–1923. <freepages.genealogy.rootsweb.com>
↵Yale College, 1906. Biographical Record of the Class of Sixty.
↵Joseph Silas Diller (1850–1928) was Dutton's principal assistant in the Division of Volcanic Geology, and became its head on Dutton's transfer to the Irrigation Survey in 1888. Diller was responsible for much of the initial geological mapping of the Cascade Range, among other things.
↵Dutton, C. E. 1871. The causes of regional elevations and subsidences. Address to the American Philosophical Society, 7 April 1871 (published as Dutton 1873).
↵Dutton, C. E. 1873. A criticism of the contractional hypothesis. Address to the Philosophical Society of Washington, Winter 1873 (published as Dutton 1874).
↵King 1880, pp. 3–7. In this report, King presents a brief historic background to the various western surveys, including the three surveys that were discontinued following establishment of the USGS.
↵King, 1880, footnote 8, pp. 6–7. King, describing the ambiguities in the congressional mandate to the USGS, explains that ‘I have entirely abandoned that plan, and have divided the region west of the 101st meridian into four geological districts.’ These districts were the divisions of the Rocky Mountains, the Colorado, the Great Basin, and the Pacific. Acknowledging that the region has been for many years the field of exploration of Powell, he further states that ‘the Division of the Colorado is intended only as a temporary one until this work, already far advanced, can be brought to completion.’
↵US Statutes at Large, 22 (7 August 1882), 329.
↵When Diller succeeded Dutton as its head on 1 July 1888, the Division of Volcanic Geology was renamed the Cascade Division.
↵Letter to Sir Archibald Geikie from Capt. Clarence Edward Dutton, 6 June 1891. Edinburgh University Library Special Collections.
↵Reprinted in Journal of Geology, 14, 259–268.
↵In his sympathetic obituary, Diller notes that Dutton smoked vigorously at his work for many years but desisted in later life.
↵Letter to Archibald Geikie from Capt. Clarence Edward Dutton, 20 January 1881. Edinburgh University Library Special Collections.
↵Letter to J. D. Dana, Washington, D.C., 8 February 1883. Reprinted as Dutton (1883).
↵Letter to J. D. Dana, Washington, D.C., 8 February 1883. Reprinted as Dutton (1883, p. 226).
↵Letter to Archibald Geikie from Capt. Clarence Edward Dutton, 21 July 1884. Edinburgh University Library Special Collections.
↵The radioactive properties of uranium had been discovered by Henri Becquerel in 1896 and of thorium, polonium and radium by Marie Curie in 1897 and subsequent years. Radioactive decay rates were soon seen by geologists as a means for redefining the age of Earth and its rocks, and for providing a source of heat within the Earth.
↵This is a brief note by Delaney concerning page 344 of volume 1 of Leonardo's notebooks, translated and edited by Edward MacCurdy.
↵An excellent summary of early ideas on this theme is provided by Watts (2001, pp. 1–17).
↵This paper was initially read before the American Philosophical Society in Philadelphia on 7 April 1871.
↵This paper was presented to the Philosophical Society of Washington during the winter of 1872–1873.
↵Stegner headed the literary department at Stanford University from 1946 to 1971, and earlier, while a student at the University of Iowa in 1932, had written a thesis on Clarence Dutton's writings.
- © The Geological Society of London 2007
