Abstract The Isle of Arran lies off the Ayrshire coast in the Firth of Clyde, SW Scotland. James Hutton visited Arran in August 1787 with his companion, John Clerk, and together they made the first geological investigation of the island. Hutton returned to Edinburgh satisfied that he had at last found the critical field evidence he had been searching for in support of his ‘Theory of the Earth’. In June 1797, ten years after Hutton's first survey of Arran, Robert Jameson arrived on the island to investigate its geology and mineralogy. Jameson was still only 22 but had already become one of Hutton's most ardent critics. The previous year he had read two papers to the Royal Medical Society of Edinburgh refuting critical elements of Hutton's ‘Theory’. Based at Kilmichael, near Brodick, on the east coast, Jameson spent most of June, July and August systematically exploring Arran entirely on foot. On returning to Edinburgh, he combined a narrative of his observations on Arran with an earlier trip to his parents' native Shetland Islands, in what became the earliest published account of the geology of Arran; An Outline of the Mineralogy of the Shetland Islands, and of the Island of Arran (1798). Jameson returned to Arran for a second, shorter visit in August 1799 and subsequently published a second book, The Mineralogy of the Scottish Isles … (1800), which presented a revised and updated geological description of Arran. Jameson's handwritten journals for both his 1797 and 1799 tours of Arran survive. In this paper we draw on these first-hand accounts of Jameson's field observations and discuss them alongside his two subsequent books describing Arran's geology. The journals clearly show that Jameson was an acute observer in the field and consistently made his interpretations in accordance with Wernerian principles. Although he had read the published Volumes I and II of Hutton's ‘ Theory ’, it appears that he had not seen the unpublished Volume III manuscript prior to either tour. Nevertheless, Jameson's exploration of the island closely follows that of Hutton's and they visited many of the same field localities. Here, we use Jameson's Arran journals to retrace his field investigations and discuss them in the light of Hutton's previous work on the island and in relation to Jameson's own Wernerian views. The difference of approach and interpretation between the two in the field on Arran mirrors the wider conflict between Plutonists and Neptunists at this time.

Abstract The Highland Border Complex refers to a variety of rock-types exposed in a scattering of much-faulted outcrops lying along the Highland Boundary Fault that extends northeastwards from the Island of Arran to Stonehaven (Fig. 3). No unified stratigraphical scheme can be applied across the outcrops, and many units have not been formally named. Curry et al. (1984) reviewed the evidence for the ages of the various outcrops, and gave references to earlier work. The present chart is based on their compilation, and summarizes some of the sections, especially those at which some stratigraphical control is available. In several instances, elements of the Complex are seen to be unconformably overlain by the Lower Old Red Sandstone, which forms the steep northern limb of the Strathmore Syncline of the northern part of the Midland Valley of Scotland. The problem of the age of the Dalradian Supergroup has been much discussed. Although the lower divisions are of Proterozoic age and recent work affirms the continuity of the Ben Ledi and Keltie Water Grit formations with the Leny Limestone of late Early Cambrian age (Harris et al. 1998; Tanner 1998), Molyneux (1998) has re-opened the possibility that a part of the uppermost Dalradian succession, including the Macduf Slates is, at the oldest, of early Ordovician age.