 The S&BR line was to leave the Slamannan main line at Causewayend, and cross the Union Canal by a moveable bridge, turning north and passing under the E&GR main line near Myrehead Farm, with one or more branches to the E&GR line near there.Relations with the E&GR became difficult at this stage, and a start on construction was frustrated for some time.In the interval the Slamannan Railway and the other "coal railways" in west Central Scotland changed their gauge from 4 ft 6 in to standard gauge (4 ft 8½ in) in July 1847, and they merged, forming the Monkland Railways on 14 August 1848.