Mont-de-Marsan, the oldest of the bastides, was founded in 1141, and the movement for founding them lasted during the 12th, 13th and 14th centuries, attaining its height between 1250 and 1350.
Loaded Batarnay with favours: he married him to a rich heiress, Georgette de Montchenu, lady of Le Bouchage; besides making him captain of Mont Saint Michel and giving him valuable estates, with, later, the titles of counsellor and chamberlain to the king.
Forbes was also interested in geology, and published memoirs on the thermal springs of the Pyrenees, on the extinct volcanoes of the Vivarais (Ardeche), on the geology of the Cuchullin and Eildon hills, &c. In addition to about 150 scientific papers, he wrote Travels through the Alps of Savoy and Other Parts of the Pennine Chain, with Observations on the Phenomena of Glaciers (1843); Norway and its Glaciers (1853); Occasional Papers on the Theory of Glaciers (1859); A Tour of Mont Blanc and Monte Rosa (1855).
He was removed to Carnarvon Castle, and thence to Mont Orgueil Castle in Jersey, where he occupied himself in writing against popery.
Not known early save as a purely local route, the Simplon Pass rose into importance when Napoleon caused the carriage road to be built across it between 1800 and 1807, though it suffered a new eclipse on the opening of the Mont Cenis (1871) and St Gotthard railways (1882).