Horace Benedict de Saussure
Saussure, Horace Bénédict De
SAUSSURE, HORACE BéNéDICT DE
(b. near Geneva [Conches], 17 February 1740; d. Geneva, 22 January 1799)
geology, meteorology, botany education.
Saussure’ ancestors emigranted to Geneva from France and Italy to escape the religious persecutions of the sixteenth century. (The name “Saulxures” is still to be found in several villages in Lorraine.) The family contained a number of writers and scientists. Saussure may have inherited his early interest in botany from his father, the agricultural author Nicolas de Saussure: from his mother, an invalid, he inherited an ability to endure hardship, a philosophical turn of mind, and a delicate constitution. He was sent to the Collège of Geneva when he was six and entered the university there when he was fourteen. During his early years he also took long walking trips in the vicinity of Geneva and in the Salève, the Voirons, and the Jura, and was strongly influenced by two naturalists, his uncle Charles Bonnet and the physician and botanist Albrecht von Haller.
Saussure completed a degree in philosophy in 1759 with a dissertation on the transmission of heat from the rays of the sun. In 1760 he made the first of a number of trips to Chamonix, on this occasion for the specific purpose of collecting plant specimens for Haller. He wrote a lyrical description of the mountains and glaciers of the area and climbed the Brévent with Pierre Simon, who served as his guide on a number of subsequent occasions. In addition, Saussure placed a notice in each of the surrounding parishes, offering a handsome reward to the first person to climb Mont Blanc.
In 1761 Saussure was a candidate for the chair of mathematics at the Academy of Geneva, but he was not elected: he therefore turned for consolation to the classical authors and continued his botanical investigations. His treatise Observations sur l’écorce des feuilles et des pétales. published in 1762, was dedicated to Haller. He presented this, together with a philosophical thesis entitled “Principal Causes of Errors Arising from the Qualities of the Mind” and a work “On Rainbows, Haloes, and Parhelia,” when the chair of philosophy at the Academy became vacant in the same year. Haller strongly supported his candidacy, and he was elected. He lectured in French on physics and natural history and in Latin on metaphysics in alternate years.
Saussure made another trip to Chamonix in March 1764. and at about this time he began to concentrate on geology, although he did not abandon botany completely. In the following year he married Albertine Amélie Boissier, who brought him a considerable fortune and a beautiful house in Geneva. His passion for mountains (he had decided both to climb Mont Blanc and to take an annual alpine tour) nevertheless remained unabated and was to become a source of anxiety to his family. In July 1767 he completed a tour of Mont Blanc. Where he carried out experiments on heat and cold, on the weight of the atmosphere, and on electricity and magnetism. In these he employed what was probably the first electrometer, an instrument that he himself had developed. He returned to Geneva for the birth of his son, Nicolas-Théodore, in October.
Saussure held liberal views that set him apart from most of his fellow patricians and professors, and in 1768 presented as a private citizen a plan for reform that advocated both a more democratic constitution and popular education. It was not accepted, and he thereupon decided to escape recurrent political crises between the aristocracy and the people of Geneva by immediately going on a “grand tour” with his wife. He spent some time in Paris, where he met Buffon (their dislike was mutual) and held discussions with a number of French geologists, including a long dialogue on the basalts of the Auvergne with Desmarest and Guettard. He also took every opportunity to attend plays. Saussure was in England by mid-summer of the same year, and visited coal, tin, and lead mines, as well as quarries, from the Midlands to Cornwall. In London he met with members of the Royal Society and discussed electricity with Benjamin Franklin. He and his wife returned to Geneva in February 1769, and Saussure refused any participation in local politics, although strongly sympathetic to the popular parties.
In the summer of 1771 Saussure made an expedition to study the lakes and flora of northern Italy: on his return trip through the Great St. Bernard he felt the first symptoms of a serious gastric illness, and by the fall of the following year his health had so declined that he was advised to spend the winter in a warmer climate. He therefore returned to Italy, Where he investigated the iron mines of Elba, then proceeded to Rome and to Naples, where Sir William Hamilton acted as his guide on a visit to Vesuvius and the Campi Phlegraei. Saussure then went on to Sicily and on 5 June 1773 climbed Mt. Etna. He found his health improved and was enthusiastic about the attractions that Italy offered to the naturalist, although he published only a few papers on it instead of the larger work that he considered.
Returning to Geneva, Saussure was appointed rector of the university, in which post he served for two years, from 1774 until 1776. He took advantage of this position to present a series of proposals for the reform of the Geneva Collège; sensitive to the popular unrest that was enveloping all Europe. Saussure felt that its effects might be dissipated by more adequate public education. His proposals led to a violent controversy, with political overtones. particularly since he had drawn on some of the ideas set out in Rousseau’s Émile, a work recently condemned at Geneva. Since his proposed reforms were not to be put into effect, Saussure tried another approach, founding the Société des Arts, in which different social classes and professions were to meet to apply the arts and sciences to industry. In 1776 Saussure served as the society’s first president.
At the same time, Saussure also began to make the extensive alpine investigations that he described in the four volumes of his Voyages dans les Alpes, précédés d’un essai sur l’histoire naturelle des environs de Genève, published between 1779 and 1796. Although he resigned his professorship in January 1786, citing ill health, the years from 1774 through 1789 marked the period of his most strenuous alpine activity. This period also coincides with an increasing involvement of Saussure in local politics. Until 1781, his proposals for political and educational reforms were personal endeavors: after that date his sense of civic duty led him to accept numerous public offices. They ranged from his election to several councils of the patrician governing system before the revolution to membership in numerous committees involved in successive changes of the form of government in Geneva and in foreign affairs immediately before, during, and after the revolution, until his voluntary withdrawal from public life in 1794 after the famous Massacre of the Bastions.
In the summer of 1787 Saussure climbed Mont Blanc, a feat that had been accomplished for Jacques Balmat and Michel Gabriel Paccard. On his won ascent, Saussure was accompanied by eighteen guides and carried a number of scientific instruments, many of them of his own design and construction. with which he undertook appropriate experiments during the four and one-half hours that he spent at the summit. The great elevation also allowed him to observe directly a number of geological features about which he had previously only been able to speculate. The success of his expedition caught the popular imagination (at one point it was even suggested that the mountain be renamed in his honor) and won Saussure an international reputation. He was elected a fellow of the Royal Society of London in April 1788, under the sponsorship of Hamilton, and in 1791 he became one of the eight foreign members of the French Academy of Sciences.
Since Saussure had had only limited time on top of Mont Blanc, he sought further opportunities to perform high-altitude experiments and observations. In July 1788, with his son. Nicolas-Théodore, he camped for fifteen days at a base 11,000 feet high on the Col du Géant. Despite precarious conditions, the two men completed a full series of observations of the daily variations of winds and other meteorological phenomena. Saussure was also able to observe geological and topographical details during the hours of dawn and sunset, the conditions under which structure is most apparent.
In July 1789, again in the company of his son, Saussure set out to measure the height of Monte Rosa and to investigate its geological structure. He made a series of observations that confirmed his neptunist ideas about the formation of granite and was greatly impressed by the sight of the Matterhorn, which he decided to measure next. While he was on this expedition, Saussure received news of the fall of the Bastille. His letters show that he maintained his liberal attitudes–indeed, he had taken part in drafting legislation designed to alleviate in Geneva the unrest similar to that which produced events in France–but he was unfortunately too optimistic about the fate of the French securities in which most of his money was invested.
Saussure contained his scientific work as the French Revolution began to make itself felt in Geneva. In August 1792, during a short period of political calm, he returned with his son to the Matterhorn to measure its altitude. This was the last trip that he recorded in his Voyages. He returned to Geneva to learn that he had lost most of his fortune and that his wife’s income had been drastically reduced. As the revolution spread to Geneva in the fall, many patrician families fled the country: Saussure remained, however, and participated in several committees that were attempting to draw up a new revolutionary constitution. In 1793 he took the voluntary oath to Liberty, Equality, and Fraternity.
Saussure once again took the opportunity to present a project for national public education, but his health had again begun to fail. He had a series of seizures that left him partially paralyzed in March 1794, yet he continued under the necessity of finding a position that would increase his income. In particular, Saussure hoped to find a professorship at a French university, perhaps combined with an inspectorship of mines, but no such position was offered him. He also considered the universities of Göttingen, Berlin, and St. Petersburg, and even an exile in the United States, where Thomas Jefferson was looking for a faculty for the new university he was organizing at Charlottesville, Virginia (Jefferson had suggested to Washington that some of the professors at the University of Geneva, especially Saussure, might be glad to find refuge and employment in America). Nonetheless, no offer was actually made to him, and Saussure remained in Geneva until his death in 1799. By 1796, when the third and fourth volumes of his Voyages were published, largely under the direction of his son, he had been entirely incapacitated by a second stroke.
Although the Voyages are a record of Saussure’s expeditions between 1774 and 1787, he did not set out the descriptions of his travels in chronological order. Rather, he abstracted and grouped the results of his journeys into three sections, of which one concerned his work in the area of Mont Blanc, another his trips through the Mont Cenis pass to the Italian and French Rivieras and his return through Provence, and the last his numerous expeditions to the area of the Gries, the St. Gotthard, and the Italian lakes. Subjects not subsumed under these general headings were given specific chapters, arranged chronologically. His book incorporated the observations that Saussure made on the spot, which he recorded instantly, then wrote up in a more finished draft within twenty-four hours. The work also reflects his method of exploration, whereby he returned to an area several times in order to complete and verify his observations.
The Voyages demonstrate Saussure’s approach toward a theory of the earth, to which end he collected data tirelessly. He had arrived at a tentative theory as early as 1774, when he had investigated only a few alpine passes. In the same year he delivered a lecture on mountain structure: although the lecture itself is not preserved, an abstract of it appears in the Voyages.
As Saussure originally conceived of the structure of the Alps, the primitive and central chain of the mountains consist of vertical strata, while the marginal or secondary mountains adjacent to the primitive mountains consist of steeply inclined beds. These progressively approach the horizontal as they reach the margins of the chain, where they are partially surrounded by tertiary mountains that are composed of the debris of all earlier deposits. It was therefore apparent to Saussure that both the primitive and secondary mountains of the chain must consist of distinct strata that display a transition in both their composition and their structure.
Saussure had accepted the notion that the secondary mountains had been formed on the bottom of the sea: he therefore drew upon the similarities between the primitive and secondary mountains to argue that the primitive mountains were also deposited on the ocean floor. The earth must therefore have been covered by a universal sea, which through crystallizations and successive deposits generated first the primitive mountains, then, around them in a series of concentric shells, the secondary ranges. The fire—or other “elastic fluids”—enclosed within the earth later lifted and ruptured the entire crust of the earth: in this process, the primitive mountains were lifted up, while the secondary ones became tilted against them. The waters of the universal ocean then rushed into the fissures left along the margins of the Alps, transporting for great distances huge boulders that were eventually scattered across the plains. Following the retreat of the waters, the germs of plants and animals, made fecund by their exposure to the air, began to develop on the newly exposed ground and in the residual water that remained in depressions of the earth.
Although Saussure stated specifically that he had arrived at his ideas without giving any thought to any particular system, it is easy to recognize in his approach the neptunist ideas associated with the contemporary school of Werner, as well as a plutonist idea of vertical movements as the result of internal fire of Cartesian origin. The concept of the universal waters rushing away from the Alps prevented Saussure from understanding the systems of frontal moraines that he observed on both sides of the mountains, although he had actually seen the recent fluctuations of glaciers in the valley of Chamonix.
After some thirteen years of accurate observations and thinking, and particularly after having studied the St. Gotthard area, Saussure concluded that the dislocation, distortion, and even overturning of the alpine rocks had been caused by processes of horizontal compression, as well as by uplifting by internal explosions. He thus came close to an accurate understanding of the structure of the Alps.
Despite his early formulation of a theory of the earth, and despite his further work toward emending this theory, Saussure never presented his material in a final, synthetic form. Why he did not do so remains a matter of some controversy. Although Cuvier, in his Éloge of Saussure, suggested that Saussure deliberately refrained from developing any theory, an analysis of the Voyages indicates that, on the contrary, Saussure fully intended to write such a synthesis until the time that he became physically disabled. It must not be forgotten that Saussure became incapacitated when he was only fifty-four; having completed his travels, he must have anticipated ten or twenty years in which he could put his data into order. Since his illness did not permit him to do so, he substituted, in the last volume of the Voyages, an “Agenda or General Compendium of the Results of the Observations and Investigations Which Are to Serve as a Basis for the Theory of the Earth,” which he characterized as a list of the problems to be solved by his followers. He thereby placed in the hands of his successors the fruits of his thirty-six years of travel and work, and left to them the task of reaching a general theory.
Saussure envisioned a theory of the earth that was to be based on uniformitarian principles, in which the present state of the earth would be carefully studied both to elucidate its past history and to predict its future. He proposed that such a theory should begin with a thorough review of the results of all previous workers and a description of the character of the various rocks (including their fossils) that compose mountain ranges. A discussion of all the fundamental laws, both physical and chemical, that affect the atmospheric envelope of the earth and play a significant role in shaping its features should then follow; finally, the successive stages of the evolution of the crust of the earth through geological time should be demonstrated by relating observations to laws.
Whether or not Saussure himself could have constructed an adequate theory within this outline remains open to question. It seems as if he was perhaps too timid in drawing conclusions and in discarding the theories of others when they were in conflict with his own observations. It is also the case that the structure of the Alps, his chief concern, was simply too complicated to be understood in the light of the geological knowledge available to the eighteenth century. Saussure himself seems to have known this intuitively, since at the end of the Voyages he noted that the only constant feature of the Alps was their variety.
Nonetheless, Saussure’s dedicated work was of great importance in the development of geology, since, among other things, it provided James Hutton with fundamental documentation. In addition, Saussure devised a number of useful instruments, among them a hair hygrometer that utilized a degreased human hair to measure humidity, and he also performed some experiments on the fusion of granites and porphyries that entitled him to be considered the first experimental petrologist. Finally, he popularized the very term “geology,” which replaced “geognosy” in the 1770’s and 1780’s.
I. Original Works. Saussure’s major work is Voyages dans les Alpes, précédés d’un essai sur l’histoire naturelle des environs de Genève, 4 vols. (Neuchâtel–Geneva, 1779–1796, and later eds.), repr. in facsimile (Bologna, 1969).
See also Dissertatio physica de igne (Geneva, 1758): Observations sur l’écorce des feuilles et des pétales des plantes (Geneva, 1762); “Description des effets du tonnerre, observés à Naples dans la maison de Mylord Tilney,” in Observations sur la physique, 1 (1773), 442–450; Projet de réforme pour le Collège de Genève (Geneva, 1774); Eclaircissemens sur le projet de réforme pour le collège de Genève (Geneva, 1774); Essais sur l’hygrométrie (Neuchâtel, 1783); “Lettre à Son Excellence M. le Chevalier Hamilton ... sur la géographie physique de l’Italie,” in Observations sur la physique, 7 (1776), 19–38; “Lettre de M. de Saussure à M. Faujas de Saint-Fond,” in Faujas de Saint-Fond, Description des expériences de la machine aérostatique de M. M. de Montgolfier, II (Paris, 1784), 112–127; “Lettre de M. de Saussure à M. l’Abbé J. A. Mongez le jeune, sur l’usage du chalumeau,” in Observations sur la physique, 26 (1785), 409–413; Relation abrégée d’un voyage à la cîme du Mont-Blanc (Geneva, 1787); “Défense de l’hygromètre à cheveu,” in Observations sur la physique, 32 (1788), 24–45, 98–107, and repr. separately (Geneva, 1788); “Description d’un cyanomètre ou d’un appareil destiné à mesurer la transparence de l’air,” in Memorie della R. Accademia delle scienze di Torino, 4 (1788–1789), 409–424; and “Description d’un diaphanomètre ou d’un appareil destiné à mesurer l’intensité de la couleur bleue du ciel,” ibid., 425–453.
See further “De la constitution physique de l’Italie,” in J. J. F. de Lalande, Voyage en Italie ..., 1 (Geneva, 1790), 45–48; “Description de deux nouvelles espèces de trémelles douées d’un mouvement spontané,” in Observations sur la physique, 37 (1790), 401–409; Éloge historique de Charles Bonnet (Geneva, 1793); Rapport et projet de loi du Comité d’Instruction Publique. Lu à l’Assemblée Nationale le 9 août 1793 par les citoyens Dessaussure et Bourrit fils (Geneva, 1793); “Sur les collines volcaniques du Brisgau,” in Journal de physique, 1 (1794), 325–362: “Notice sur la mine de fer de Saint-George en Maurienne,” in Journal des mines, 1 , no. 4 (1794), 56–61; “Agenda ou tableau général des observations et des recherches dont les résultats doivent servir de base à la théorie de la terre,” ibid., 4 , no. 20 (1796), 2–70, and repr. in last vol. of Voyages and separately as Agenda du voyageur géologue tiré du 4ème volume des “Voyages dans les Alpes” (Geneva, 1796); “Mémoire sur les variations de hauteur et de température de l’Arve,” in Journal de physique, 4 (1798), 50–55; and Voyages dans les Alpes, partie pittoresque des ouvrages de H. B. Saussure, with intro. by A. Sayous (Geneva-Paris, 1834).
Saussure’s letters to his wife have been published as Lettres de H. B. Saussure à sa femme, annotated by E. Galliard and H. F. Montagnier (Chambéry, 1937).
II. Secondary Literature. On Saussure and his work, see Georges Cuvier, “Éloges historiques de Charles Bonnet et H. B. de Saussure,” in Recueil des éloges historiques lus dans les séances publiques de l’Institut Royal de France, II (Strasbourg-Paris, 1819), 383–430; Douglas W. Freshfield and H. F. Montagnier, The Life of Horace Bénédict de Saussure (London, 1920): and Jean Senebier, Mémoire historique sur la vie et les écrits de Horace Bénédict de Saussure, pour servir d’introduction à la lecture de ses ouvrages (Geneva, 1801).
Albert V. Carozzi
Saussure, Horace BénéDict De
SAUSSURE, HORACE BéNéDICT DE
(b. near Geneva [Conches], Switzerland, 17 February 1740; d. Geneva, 22 January 1799), geology, meteorology, botany, education. For the original article on Saussure see DSB, vol. 12.
When Saussure died in 1799, his personal archives were given by the family to the public and university library of Geneva where they were left untouched until 1975 when the author of this postscript decided to study the numerous manuscripts brought to light and discovered astonishing conditions. The only printed version of his work was available under the title Voyages dans les Alpes…(1779–1796). The general reader was in a rather strange situation for more than two centuries. It was as if Saussure, the founder of Alpine Geology, had gathered an enormous amount of observations throughout his entire life from which nothing new pertaining to the fundamental mechanisms that built the Alps was extracted.
The Voyages dans les Alpes … The major obstacle originates from the fact that Saussure could not describe all his travels without needless repetitions. Therefore he made the choice of preparing a pastiche consisting of the best descriptions organized into seven ideal voyages dealing with the major massifs, valleys, and structures regardless of the dates of their best original description. Interspersed in the narrative are very short sections dealing with theoretical interpretations, but they are too short and cryptic to give real clues on the evolution of the author’s thinking. Consequently, it is not possible to unravel the path of his geological thinking. Not enough appears to have been provided besides the repetition of the statement that more observations were needed and that the major theoretical discussions would be postponed. The main focus was a final theory of the Earth. Unfortunately his poor health prevented him from writing, and he died in 1799. Only two abbreviated tables of contents were published in 1786 and in 1796 respectively.
More than two centuries passed during which Saussure fell into oblivion or was designated with the unwarranted label of a simple observer while hundreds of his field-note booklets and other manuscripts were carefully preserved but remained unstudied. These texts contain in perfect chronological order the detailed account of the discovery of a major principle of structural geology as demonstrated by Saussure in the Alps and accepted in the early twenty-first century as fundamental in mountain building in general—horizontal overthrusting. From time to time the non-scientific portions of the Voyages dans les Alpes… were republished by anonymous editors to satisfy the curiosity of the general public under the title of Partie Pittoresque des Voyages de M. de Saussure.
Saussure undertook important field trips outside the Alps and their related manuscripts concerning the basalt in Italy (1772–1773), in Auvergne and Vivarais (1776), and other places in Europe also contain critical data. The same is true for his lecture notes on physical geography at the Academy of Geneva (1775) and many aspects of physics and metaphysics that remain to be evaluated.
The Manuscripts in Chronological Order Saussure’s manuscripts were written mostly in the field in pencil and finalized within at least twenty-four hours in pen every day. This remarkable suite of observations represents a perfect time sequence from which the evolution of his geological interpretations can be obtained. Saussure’s notes are in French and occasionally in Latin. The original language was followed by an English translation and footnotes explaining the geological problems in ancient and modern terms and by following his itineraries step by step. Overlapping dates of the manuscripts results from the fact that Saussure investigated various subjects simultaneously during a given period of time.
Early Alpine Structure Concepts These observations (Ms 1760–1775) pertain to the structural features of the Salève mountain overlooking Geneva, those of the Jura Mountains at the Dôle, and between Pontarlier and Besançon. The problem common to these folds was to understand the cores of the structures made of vertical limestone beds pushed upwards through younger strata leaning against them at variable angles (so-called folds in A). Other parts of the High Calcareous Alps display spectacular S-shaped folds (such as at the Arpenaz Cascade) forming recumbent structures with adjacent cavities in the landscape left open when the limestone beds were folded upon themselves.
Saussure was confused by all this structural complexity. For the time being he proposed a variety of interpretations that cover the whole spectrum of unsupported theories of his time. These included a kind of crystallization on the seafloor generating structures comparable to the microscopic folds of agate concretions or subterranean forces of unknown origin, or even subterranean fires although no traces of their action was visible.
The Cramont and Vallorcine Saussure proposed a new mechanism (Ms 1774–1778) derived from the panorama as seen from the summit of the Cramont (a peak located immediately south of Mont-Blanc). According to him, the primitive and secondary rock layers were deposited horizontally on the seafloor. The explosion of elastic fluids in subterranean caverns uplifted the primitive rocks in a vertical and contorted position while cutting across the overlying secondary rocks. These secondary rocks remained leaning against the primitive ones at an angle that decreased gradually away from the center of the Alps. The originality of this approach was in the vertical force due to the explosion of the elastic fluids that left no traces. An earlier theory using the action of fire was eliminated from the working hypotheses by Saussure’s new theory.
Saussure then tried to characterize his concept of vertical force by investigating the various types of conglomerates, in particular those of Vallorcine (near Chamonix),
Horace Bénédict de Saussure . Horace Bénédict de Saussure, circa 1760. ROGER VIOLLET COLLECTION/GETTY IMAGES .
that were in the critical intermediate position between the vertical primitive rocks and the tilted, overlying secondary ones. These conglomerates displayed huge and spectacular angular to rounded boulders of granite in a purple, shaly matrix. This unusual rock type was interpreted by Saussure as indicating a powerful process of fragmentation followed by redeposition according to the size of the clasts in a quiet aqueous environment. These depositional events were followed in time by the general uplifting of the beds. The final conclusion reached was that these conglomerates represent the product of violent earthquakes and consequently that mountain building is a seismic process. This interpretation is a theoretical challenge still under consideration by modern geologists. Unquestionably, Saussure was well informed about the spectacular effects of the numerous earthquakes of his century from reading books and periodicals.
Saussure’s Scientific Library From the early part of his career, Saussure had been deeply concerned about being up-to-date with the progress of the various sciences of interest to him, in particular geology and mineralogy, but also botany, chemistry, astronomy, physics, mathematics, and philosophy. By wisely using his personal wealth he began to assemble a systematic library. Two catalogs in his own hand (Ms 1788–1797) show holdings of at least 1,202 items, that is 1,143 books and 59 periodicals published by learned societies from all over Europe. Rapidly, it became one of the most diversified collections of the eighteenth century. Related correspondence with major book dealers of Europe reveals an extensive network of purchases and sales. He bought between 1760 and 1768, 1,034 volumes, that is, sixty-five percent of the final library he needed for his research. The major reason for such a collection lies in the fact that Geneva was a relatively isolated city-state and that purchasing books was the only way to keep abreast with scientific development in all fields. However the French Revolution and its turmoil led to the loss of Saussure’s fortune, and many precious holdings were sold at auction to his profound chagrin.
Basaltic Volcanism Saussure wrote a series of manuscripts on the origin of prismatic basalt in Italy, Auvergne, Vivarais, Provence, and Brisgau (Ms 1772–1798). In particular, he wanted to see for himself the examples described in the Massif Central of Auvergne by Nicolas Desmarest who had demonstrated the volcanic origin of basalt by following large prismatic lava flows from the plains up the slopes of scoriaceous cones into the corresponding craters.
Saussure returned from his trip to Auvergne an enthusiastic believer in the volcanic origin of basalt. However, through the years of investigating rather superficially many outcrops, and by accepting the neptunian ideas of Abraham Gottlob Werner, he tempered his position to the extent of assuming two types of basalt: an aqueous deposit and a volcanic lava. Eventually, he believed only in a water-laid origin. In defense of these strange changes of concepts it should be pointed out that Saussure happened to come across many unusual types of basalt that he did not study in sufficient detail. Furthermore he was a famous geologist who had to take a position in the controversy. He took the erroneous one as demonstrated by James Hutton who introduced the modern ideas on the subject at the time of Saussure’s death.
Lectures on Physical Geography The documents pertaining to physical geography (Ms 1775) are of three major types. A first version written in French on index cards that is the most personal document and a second version in Latin also on note cards—now lost—which is the required language of the oral academic presentation. The third version is a complete Latin text, not from Saussure’s hand but a manuscript carefully copied in 1786 by one of his students, Jacques-Louis Peschier. Among the references in this unique manuscript two famous works are constantly quoted, criticized, or praised without restrictions, namely George-Louis Buffon’s Théorie de la Terre (1749) and The Physikalishe Beschreibung of Olof Torbern Bergman (1766). Of great interest is the spontaneous presentation of the index cards in French which has a completely informal style with so-called red flags reminding the speaker to attract the attention of the students to important aspects of the presentation. A similar technique is still used by experienced lecturers.
Horizontal Thrusting in Opposite Directions These manuscripts (Ms 1780–1784) pertain to a large structure of tertiary sandstones (Molasse) of Albi-sur-Chéran: Saussure briefly looked at this structure in 1780. He observed that at this location it could only be formed by horizontal thrusting in opposite directions—a new concept given without any further comments. Returning to the field in 1784 and after detailed studies he presented a speculation of great importance. According to Saussure horizontal thrusting in opposite directions implied not only a detachment (décollement) of the Earth’s crust from its substratum, but also a general shortening of the seismic system and finally present-day antagonistic stresses that maintain the Alpine structures at their high elevation. The date of this critical observation was 13 October 1784. He even went so far as to suggest laboratory simulations with clay layers, becoming a pioneer of experimental geology.
It is difficult to understand such a concise discussion of a fundamental concept without much consideration, and Saussure’s style does not help. It can be better explained by a modern interpretation using a transverse cross-section trending through the Valley of Chamonix and the summit of Mont-Blanc. If overthrusting tilted the rocks from an original horizontal position to their present vertical one and the bottom of the Valley of Chamonix represents the ancient surface of the crust then the horizontal distance between the Chamonix Valley and the top of Mont-Blanc corresponds approximately to the thickness of the crust that has been overthrusted. Therefore, the summit of Mont-Blanc, which reaches in the twenty-first century the elevation of about one league over the present surface of the globe, was originally buried at a depth of more than two leagues (8.8 kilometers) below that surface.
The Alps and World Mountains In summary, Saussure (Notes of 6 July 1795) considered a worldwide application of his structural ideas to the origin of the great orogenic belts. He stated that it is not at the great depth of coal mines but on the top of mountains consisting of vertical beds uplifted in such a position and maintained in it by the permanent stresses of earthquakes, that lie the answers of modern tangential tectonics.
Carozzi, Albert V. “Découverte d’une grande découverte:Horace-Bénédict de Saussure et les refoulements en sens contraires dans la formation des Alpes.” In Les Plis du Temps, mythe, science et H.-B. de Saussure, edited by Albert V. Carozzi, Bernard Crettaz, and David Ripoll. Geneva: Collection Nouveaux Itinéraires Amoudruz, No. 5, Musée d’Ethnographie de Genève, Annexe de Conches, 1998.
——. Manuscripts and publications of Horace-Bénédict de Saussure on the origin of basalt (1772–1797). Bilingual Volume. Geneva: Editions Zoé, 2000.
——. Horace-Bénédict de Saussure (1740–1799): Un pionnier des sciences de la Terre. Geneva: Editions Slatkine, 2005. This is the most recent biography.
———, and Gerda Bouvier. The Scientific Library of Horace Bénédict de Saussure (1797): Annotated Catalog of an 18th-Century Bibliographic and Historic Treasure. Mémoires Société de Physique et d’Histoire Naturelle de Genève, vol. 6, 1994.
——, and John C. Newman. Lectures on Physical Geography Given in 1775 by Horace-Bénédict de Saussure at the Academy of Geneva. Trilingual volume. Geneva: Editions Zoé, 2003.
Albert V. Carozzi