HISTORY OF GEOLOGY STUDENT AWARD: GEORGIUS AGRICOLA'S CONTRIBUTIONS TO HYDROGEOLOGY

Georgius Agricola (1494-1555) is best known for helping found modern economic geology and mineralogy, but his work in both fields was based on his ideas about the movement and origins of groundwater. His influential writings on the subject, once well known and used by Boyle, Steno, Kircher, and Werner, have fallen into obscurity in the last two centuries.

Agricola’s De Ortu et Causis Subterraneorum (Of the Sources and Causes of Things Underground, 1546), though keeping close to the medieval tradition in many respects, nevertheless contained some important new concepts. Among them are the first known statement of the erosional cycle; advances in the description of mechanisms of fluid storage and transport; the first concept of water-rock interaction; the novel hypothesis that fluid pressure could fracture rocks; and the first hint of the slowness of geological processes. Though Agricola himself did not develop many of them fully, they opened new fields to later work. They led to quantitative evaluations of the hydrologic cycle by Palissy and Perrault; to the principles of sedimentation of Palissy, Peiresc, and Steno; to Steno’s and Kircher’s understanding of the importance of erosion; to Perrault’s concept of magma motion through the earth; and Boyle’s studies of natural solution chemistry.

Besides planting these early seeds of later geological theories, Agricola helped science in general by replacing authority with observation in his procedure. For instance, he showed by water infiltration into the local Saxon mines that water penetrates much farther into the ground than the ten feet Seneca alleged. He reasoned that the giant “receptacula” that Aristotle and his followers believed stored water underground had never been observed, and that water was more probably stored in pores in the rock. Its interaction with the host rock, he theorized, dissolved and precipitated minerals. This was the concept he later articulated into the theories of mineral and ore deposit formation in his more famous De Re Metallica (posth., 1556) and De Natura Fossilium (1546). Although not correct in all particulars, Agricola’s meticulous study and his emphasis on observation represented a major advance for hydrogeology, and deserve to be better known by geologists, who daily use the theories he helped to develop.