GEIKIE AND JUDD, AND CONTROVERSIES ABOUT THE IGNEOUS ROCKS OF THE SCOTTISH HEBRIDES - THEORY, PRACTICE, AND POWER IN THE GEOLOGICAL COMMUNITY

An account is given of one of the most heated controversies in ninetee nth-century British geology-the battle between Archibald Geikie and Jo hn Judd concerning the interpretation of the Palaeogene igneous rocks of the Inner Hebrides, particularly those of the Cuillins and the Red Hills of Skye. The controversy erupted in the first instance over the question of the respective 'territories' of the two geologists, then d eveloped into disagreement as to the origin of the plateau lavas of Sk ye: were they formed from fissure eruptions (Geikie's view) or from th e outpourings of great volcanoes (Judd's view)? Debate then focused on the question of the relative age of the gabbro of the Cuillins and th e granite (granophyre) of the Red Hills. A certain locality at Druim H ain (Druim an Eihdne) at the junction between the two rock-types becam e crucial for the dispute. Following earlier observers, Judd held that the granite was older and had been intruded by the gabbro. Geikie too k the opposite view. Geikie's work relied particularly on field observ ations, for which he was assisted by several other geologists. Judd, w ho worked by himself rested his argument more on the evidence furnishe d by petrology, using thin sections. Both geologists were influenced b y Ferdinand von Richthofen. Geikie's work appeared to be vindicated in his own lifetime by the map work of Alfred Harker, which effectively closed the controversy. But later commentators such as Walker hold tha t in a sense both were correct. There were indeed great volcanoes acti ve in the Inner Hebrides in the Palaeogene, as well as fissure eruptio ns. Moreover, recent mapping does not support all the observations of Geikie and Harker. The controversy illustrates different styles in nin eteenth-century geology, with petrological arguments, based on the exa mination of thin sections, pitted against field observations. It may a lso be seen as being linked with the ongoing rivalry in the nineteenth century between the members of the Geological Survey (particularly th e Directors General) and the 'amateur' university geologists. Geikie p revailed in the debate in part because he was able to draw on more res ources for its prosecution, being helped by various friends and member s of the Geological Survey. The study draws on the newly discovered Ge ikie archive at Haslemere, which contains his complete outgoing offici al correspondence, and 27 of his field notebooks, previously missing. With the help of this material, it is possible to gain a clearer insig ht into the methods deployed by Geikie in his fieldwork, and his ways of working and thinking.