Bischof, Carl Gustav Christoph
Bischof, Carl Gustav Christoph
(b. Wörth, near Nuremberg, Germany, 18 January 1792; d. Bonn, Germany, 29 November 1870)
Bischof probably acquired his interest in natural sciences from his father, a teacher of natural history and geography. He attended the University of Erlangen, where he obtained the doctorate and became Privatdizent in chemistry and physics. He received much early encouragement and inspiration from Nees von Esenbeck and Goldfuss. With the latter he published a two-volume physical and statistical description of the fichtelgebrige, a mountain range near Nuremberg (1817). His next work, written with Esenbeck and Rothe, dealt with the evolution of plants. His first independent book was the Lehrbuch der Stöchimometrie (1819). In the same year he was called to the newly founded University of Bonn, where he became professor of chemistry and technology.
For the rest of his life he concentrated on the chemical changes accompanying geological processes, first i the Rhineland and later in other German areas and even foreign regions. His main interest at first was the volcanic phenomena of the Eiffel and neighboring areas—specifically, the springs in these areas, which he interpreted as being largely of volcanic origin. In 1824 he published die vulkanischen Mineralquellen Deutschlands und Frankreichs, a work that aroused much interest and led to his being considered one of the main defenders of volcanistic theories (asopposed to the neptunistic). He corroborated his ideas on the origin of springs by a case study of the mineral spring of Roisdorf (1826).
The chief work of his volcanistic period was Wärmelhre des Innern unsure Endkörpers (1837). In this work he presented a critical compilation of all that work known at the time, together with many of his own observations made on the thermal properties of the earth’s surface, including observations made in mines. From these he derived his theories of thermal gradients, which were essentially correct, and his ideas on the origin of volcanism and the heat required for his kind of “metamorphic” transformation. He concluded that the observed heat gradients explained satisfactorily all known volcanic activity, as well as spring and earthquakes. The evidence presented in this book was used immediately to support the plutonist theories dominant at the time. It also included experimental evidence; the volume reduction observed during the cooling of melted basalt inspired Élie de Beaumont to propose that folded mountain chains arose from wrinkling of the surface of the contracting earth, assuming that the earth had once been in a state of fusion.
Bischof had an interest in and talent for communication his ideas to the general public. This is shown in his popular lectures, many of which are collected in Populäre Vorlesungen über naturwissen-schaftliche Gegenstäde (1842–1843) and Populäre Brief and eine gebildete Dame über das gesammte Gebiet der Naturwissenschaften (1848–1849). Bischof was not only a gifted experimentalist; he also had a flair for translating scientific knowledge into practical use. For example he was the first to harness the HCO3 spring in the volcanic areas of the Niederrhein for industrial purposes. He also promoted the recovery of copper from very low-grade ores by an expensive leaching and “cementation” method.
In 1848 Bischof began to publish his Lehrbuch der chemischen und physikalioschen Geologic, the main source of his fame. The second edition, with a supplement, ran to 3,005 pages, and was published between 1863 and 1871. It was in many ways a continuation rather than a new edition. This enormous work soon became the standard geochemical text. It appeared to support a new school of thought, the “neoneptunistic.” At the beginning of the first volume Bischof was still a plutonist and opposed neptunist views, although somewhat hesitantly. The intensive studies he made in connection with the Lehrbuch, however, convinced him more and more of the validity of the role of surface waters.
Bischof was and remained in many ways basically a laboratory chemist, despite his great interest in natural phenomena. This was his weakness in many instance, and the reason for his strong adherence to plutonsim-volcanism until about 1846 and his fervent advocation of opposite views after this time.
Just as the exaggeration of the magmatichydrothermal theory of the formation of rocks and ore deposits was in part caused by one-sided experiments between 1900 and 1960, Bischof during his time exaggerated the role of water in his experiments, extrapolating from laboratory results to natural phenomena without adequate support from observations in nature. In this manner he assumed numerous transformation of sediments to crystalline schists, gneisses, and granites—and even basic igneous rocks—of ten without even discussing field relations. He rejected plutonic metamorphism and assumed that all metamorphic processes were caused by hydrochemical (“neptunic or katogene”) reactions, i.e., changes at surface temperatures caused by a continuous flow of water through the rocks and introduction and subtraction of material. He was, in this respect, a forerunner of the extreme transformationists who, a century later, insisted upon similar transformations of sediments into various igneous rocks, usually without knowing of Bischof’s work. He also believed that oreveins had been formed from descending solutions or by lateral secretion.
Bischof’s work benefited several branches of geology and promoted a more scientific approach to many geological problems, such as the use of analogies with experiments (even though his geological theories were of ten proposed on the basis of laboratory evidence rather than field relationships). In 1849 he introduced rather than field relationships). The so-called oxygen coefficient into chemical comparisons of rocks by using the ratio between oxygen in bases and oxygen in SiO2. He offered experimental evidence for causes of landslides in 1846 and 1863.
Bischof determined the relationship of gypsum and anhydrite and proposed a connection between crystallization and climate in the Dead Sea. He recognized that gypsum is not the end of salt deposition, but the beginning of a new sequence. He argued that since gypsum and halite are the first salts to precipitate during evaporation of seawater, calcareous sediments must have been formed through the action of organisms. He also recognized that dolomitization must have taken place and assumed magnesium bicarbonate to be a major cause. Bischof did not succeed in reproducing dolomitization in the laboratory, but was able to explain cavernous limestones and the lack of fossil shells in dolomites by leaching of dolomites. He also found, in 1864, that phosphoric acid accumulates in bones, shells, and the soft parts of animals. As early as 1829 Bischof had obtained melnikowite precipitates experimentally, and in 1863–1866 he discussed the different reactions by which gypsum or anhydrite forms in one case, and in another native sulfur is precipitated. Thus he contributed to the fundamental knowledge that decades later led to the suggestion that massive stratiform sulfide deposits may be sedimentary or exhalative-sedimentary.
I. Original Works. Bischof’s major work is Lehrbuch der chemischen und physikalischen Geologie, 3 vols. (Bonn, 1846–1855; 2nd. ed., 3 vols. and supp., 1863–1871), trans. into English by B. H. Paul and J. Drummond as Elements of Chemical and Physical Geology, 3 vols. (London, 1854–1859). His other writings include Physikalisch-statistische Beschreibung des Fichtelgebirges, written with A. Goldfuss, 2 vols. (Nuremburg, 1817); with Nees von Esenbeck and Rothe, Die Entwicklung der Pflanzensubstanz (Erlangen, 1819); Lehrbuch der Stöchiometrie (Bonn, 1819); Die vulkanischen Mineralquellen Deutschlands und Frankrichs (Bonn, 1824); Die Mineralquellen von Roisdorf (Bonn, 1826); Wärmelehre des Innern unseres Erdkörpers (Bonn, 1837); also trans. into English (1844); and Populäre Vorlesungen über naturwissenschaftliche Gegenstände (Bonn, 1842–1843).
II. Secondary Literature. Works on Bischof are F. Behrend and G. Berg, Chemische Geologie (Stuttgart, 1927); V. von Cotta, Geologie der Gegenwart, I (leipzig, 1866), 61–62, 347–372; W. Fischer, Gesteins- und Lagerstättenbildung im Wandel der wissenschaftlichen Anschauung (Stuttgart, 1961); C. W. von Gümbel, in Allgemeine Deutsche Biographie, II, 665–669; Poggendorff, I, 202; and K. von Zittel, trans. by Maria M. Ogilvie-Gordon, History of Geology and Paleontology (London 1901).
G. C. Amstutz