b"Divination: A geophysicist's viewFeatureEmpowered woodsAntiquity regarded some woods as magic materials. Fruit bearing trees such as the hazel (nuts) and the oak (acorns) were thought lucky. Actions performed with their branches passed on that luck. Tacitus (AD 56-117+) in his Germania reported that the German tribes cut slips from a branch, marked them, cast them onto a white cloth, and then interpreted three chosen slips for signs of approval or disapproval of a proposed activity (frequently of a lethal kind). At summer solstices, after sunset, Scandinavians laid slips of mistletoe to identify subsurface treasure which, if there, moved the slips. Cicero in his De Officiis Figure 5.Three very influential pioneers of early-modern science interested wistfully invoked the virgula divina as a magic wand to supplyin divining: (left) Georgius Agricola German physician, (middle) Robert Boyle every want and comfort. The virgula divina was the originalEnglish Scientist, and (right) Athanasius Kircher German Jesuit polymath. divining rod but virtually nothing reliable was written aboutAgricola published several landmark works on mining (notably De Re Metallica), it in antiquity, the dark ages, and medieval times. However,economic mineralogy, and geology. Boyle founded modern chemistry and it must have been in use for a long time before it appeared,made advances in the field of early experimental physics. Kircher was an fully functional, in Germany during the Renaissance. In 1518inventive and versatile scholar who contributed significantly to geological it was denounced by Luther as a satanic violation of the firstknowledge (Mundus Subterraneus). All had outstanding intellectual abilities. commandment. Later it was for the first time discussed byThe three had direct experience of divining and were well aware of the divine. Agricola in his monumental mining text De Re Metallica. Figure 4Their attitudes to divining differed (see text).depicts a dowser wandering around the ground above a mine.Prospecting in 16 thcentury Saxony-BohemiaWe shall now discuss Renaissance attitudes to divining. The views of three outstanding early modern scientists are worthyIn a region of Europe, about 200 km south of Berlin and 100 km of attention: Georgius Agricola, Robert Boyle, and Althanasiusnorthwest of Prague, lie the Ore Mountains, the Erzgebirge, Kircher. Agricola, an empiricist, was a brilliant and thoroughof old Saxony-Bohemia. In mines of this region, polymetallic synthesiser of mineralogical data and mining practice. Boylesulphide and oxide mineralisation hosted by veins and veinletted was a gifted investigator, a great experimenter, and skilledstockworks, in and around granitoids, gneisses, and felsics, were in analysis. Kircher was a gadfly polymath, cerebral andextracted and processed, for centuries. Georg Bauer (1494-1555), a imaginative, and very influential in his time (Figure 5). respected physician in a local town, studied the local mineralogy, exploration, and mine practice, documenting his findings in several books under his Latinised name Georgius Agricola. His De Re Metallica, with its wonderful woodcut illustrations, was published in 1556. As learning revived and emerged from the medieval mindset, Agricola was one of many able men and women who objectively and accurately documented matters in which they were interested, and which they personally and carefully investigated. Agricola carried out such a study on prospecting, including divining, in the Erzgebirge.The town of Freiberg, on the northern flanks of the Ore Mountains, was mentioned by Agricola as having risen to prominence because of its silver-lead mines. Freiberg, later, through its Mining Academy, became the centre for European exploration and mining geology. The mineralisation here was typical of the prospecting targets in the 1500s, so is used as an example in the article. The Freiberg steeply inclined fissure vein system was discovered by chance around 1170 when a torrent of rain cleaned out wagon wheel ruts, exposing a mineralised vein.The vein mineralogy included galena (PbS), pyrite (FeS 2 ), ruby (native) silver (Ag), argentite (Ag 2 S), cassiterite (SnO 2 ), magnetite (Fe 3 O 4 ), haematite (Fe 2 O 3 ), other sulphides, and quartz, carbonates, and barite. The mineralisation was generally low grade but enriched at the intersection of fissure veins. The shallow oxidised ores were rich in native silver and argentite. The host rock was biotite gneiss.Agricola called these steeply inclined fissure veins vena profunda (profunda: deep, Figure 6). Vein width ranged from 5 cm to over 1 m. Vein spacing was roughly of the order of tens to hundreds of metres. The more valuable argentiferous veins had a N-S to Figure 4.A mining and prospecting scene in 16th century Saxony-Bohemia.NW-SE strike. The veins can be conveniently grouped as silver- This woodcut is from the 1580 edition of Agricolas De Re Metallica. Below,lead, quartz-lead, barite-lead, and barren, as shown in Figure7. sweating miners hammer, tunnel, raise and truck ore. Above a dowser roams,The ores probably lacked salient physical properties except forked twig erect, to conjure up more mineralisation. perhaps for a high conductivity in pods of ruby silverargentite DECEMBER 2020 PREVIEW 50"