Interpreting the Landscape - Changing Times and Ideas
The Parallel Roads provided easy routes for travellers in a region where communication was difficult, long before road building began early in the 18th century. They were attributed variously to the activities of the mythical Gaelic hero-giant Fingal (of Fingal's Cave fame) and to the work of the early Kings of Scotland. Certainly by the late 18th and early 19th centuries the Parallel Roads were one of the sights of Scotland and were being visited by the local gentry such as the Grants of Rothiemurchus, as recorded in 'Memoirs of a Highland Lady'.
The controversy over the formation of the Parallel Roads illustrates the development of science in the light of two 19th century discoveries; that sea-level can rise and fall in response to earth movements and that glaciers had existed in Scotland in the geologically recent past. The view that the Parallel Roads were old marine shorelines was championed in 1838 by the young Charles Darwin, who, fresh from his voyage to South America, had been deeply impressed by the uplift of the Chilean seashore by recent earthquakes. The originally less popular view, that the Roads were lake shorelines, came to prominence very shortly afterwards following the visit to Scotland of the Swiss geologist Louis Agassiz in 1840. Agassiz suggested a key mechanism for the otherwise puzzling formation of lakes in these glens, damming by glacier ice; this was put on a firm footing by Thomas Jamieson some 20 years later. The interest in the Parallel Roads extended to government circles, and the Ordnance Survey diverted some of its effort into specially surveying the Parallel Roads, showing that they were indeed (almost) horizontal and could be lake shorelines.
Historically, also, the landforms in Glen Roy and Glen Spean, near Loch Treig, played a key part in convincing Agassiz of the reality of the former existence of glaciers in Scotland. They provided crucial field evidence that he needed to confirm the theory of a great ice age. Following his visit, he sent a now famous letter from Fort Augustus, announcing publically the glacial theory. This world exclusive appeared in The Scotsman on 7th October 1840.