were to be dug, one for the two tracks, a drainage tunnel and a ventilation tunnel. A diameter ventilation tunnel was dug as the pilot heading. Some 38 million bricks were used for the construction of the main tunnel. When the tunnel was opened, fans on both banks changed the air in the tunnel every seven minutes. The geology of the riverbed meant that the plans were changed and at the deepest section the drainage and ventilation tunnels combined. The grade on the Liverpool side was increased to 1 in 27. Estimates of the influx of water varied from to per minute; after the works were completed the maximum pumped out of the tunnel has been per minute. There were two pumping stations, Shore Road Pumping Station on the Birkenhead bank near Hamilton Square and Georges Dock Pumping Station on Mann Island on the Liverpool Bank. The Railway's Workshop was built next to Birkenhead Central; stabling was also provided at Birkenhead Park. Opening and extensions The Mersey Railway was formally opened on 20 January 1886 and public services started on 1 February. The route had four new stations: Green Lane, Birkenhead Central and Hamilton Square in Birkenhead and James Street station in Liverpool. Green Lane and Birkenhead Central were below ground level in open cuttings whereas James Street and Hamilton Square were deep underground and accessed by lifts. In 1888 a branch tunnel to Birkenhead Park station opened, with a connection to the Wirral Railway. This was followed in 1891 by an extension from Green Lane to bay platforms at the Birkenhead Railway's Rock Ferry station, and in 1892 the tunnel was extended from James Street to a new underground station at Liverpool Central. The railway opened with steam locomotives hauling four-wheeled -long wooden carriages, with first-, second- and third-class accommodation provided in unheated compartments. In 1900 in the peak periods trains left the Rock Ferry terminus every minutes and the Birkenhead Park terminus every 15 minutes, giving a train every 5 minutes between Hamilton Square and Liverpool Central. At off-peak times this was reduced to a train every minutes, alternately from the Rock Ferry and Birkenhead Park branches. The scheduled journey time between Rock Ferry and Central was 14 minutes; between Birkenhead Park and Central, 10 minutes. As well as some through working of carriages from the Wirral Railway at Birkenhead Park, in the summer of 1899 a through