The Glasgow City and District Railway, an independent company sponsored by the NBR, was authorised on 10 August 1882 to make a line from the College station to Stobcross, a distance of 3 miles (5 km). The capital was to be £550,000. A connection at Knightswood enabling through running from Stobcross towards Dalmuir was included in the authorisation. The main section of the GC&DR was to be sub-surface, constructed by cut and cover. At its peak the construction had 22 tunnelling faces active. A four-platform station was to be provided at Queen Street, partly under the existing main line station. A new through station was to be provided at College, replacing the existing terminus. The Stobcross line at the west end was a goods-only dead end and this was to be transformed into a through line, with a station nearby at Finnieston. The construction was challenging in engineering terms: it was only the fourth underground line in the country. Opening The GC&DR line opened on 15 March 1886, and the company was amalgamated with the North British Railway. The passenger services that had previously run to Queen Street high level terminus were diverted to run through the new line, providing immediate relief at Queen Street. On the same day the NBR opened the short Hyndland branch from Partick Junction, providing a western terminus for some trains. On 1 August 1886 the Knightswood spur opened, and Queen Street goods depot was closed and the goods traffic transferred temporarily to the G&SWR goods station at College. Goods trains were not allowed to use the underground section, to minimise problems with the smoky atmosphere. Soon 90 trains daily were being handled in the underground section. At first the carriages were unlit, but following protests an incandescent lighting system was provided, powered from a conductor fixed to the tunnel walls. The system was patented by H S P Carswell; it was removed in November 1901. The smoky atmosphere in the tunnel sections was immediately a cause for serious complaint. Proposed solutions to vent the tunnels proved to be unacceptable to local residents, and for some years the issue remained contentious. Eventually the roof of Charing Cross station was removed. The four platforms at Queen Street low level station were lettered, A, B, C and D. Bridgeton extension In association with the GC&DR line, the NBR opened a short branch from College to Bridgeton Cross