Sydney Morning Herald on 3 July 1863. Whitton knew of the conquering of the Bhore Ghat, which posed problems very comparable to the Lapstone Monocline, both from personal and public communications. The way in which he adapted the Indian experience into a full ZigZag, approached over an exquisite, and very cheap, sandstone viaduct, was a substantial feat in world terms of railway engineering. The single track contributed to a fatal accident at Emu Plains in 1878 where eastbound and westbound goods trains collided. In 1890 signal boxes were built at both Lower and Upper Points of the Zig Zag, this was to replace the operation of pointsmen using hand levers. The Glenbrook tunnel deviation Commissioner of Railways, E. M. Eddy, decided that the ZigZag should be replaced by the deviation including a tunnel, both built around 1890. The Lapstone ZigZag and Lucasville station were officially closed on 18 December 1892 and the rails were raised, after the completion of the Glenbrook Tunnel Deviation. The Deviation soon experienced problems as it was built at the same too steep grade as the Zig Zag which caused the locomotives to slip in the tunnel, mostly due to water leaking onto the tunnel floor from nearby creek, and smoke also became a problem for uphill trains, as the tunnel was not designed to vent the smoke. The building of the tunnel is the subject of Arthur Streeton's famous painting Fire's On. Twentieth century By 1910, the line as a whole was being duplicated (made into double track) and the "rathole" tunnel was replaced on a different deviation with a gentler alignment with 1 in 60 (1.67%) grades and the new Glenbrook Tunnel at Bluffs point on the Glenbrook Creek escarpment. From then on the lower section of the track, including the historic Knapsack Gully Viaduct, was converted into a road, the Great Western Highway, the main road up the Lapstone hill until the M4 motorway replaced it in 1993. The older tunnel was converted for mushroom growing but was also used by the RAAF for storage during World War II. During 1943 to 1946 the Glenbrook tunnel stored chemical weapons, mainly of bulk drums of mustard. Today the Zig Zag, Knapsack Viaduct, The Old Glenbook Tunnel, and Lucasville station can all be accessed by walking tracks. Knapsack Viaduct, 1863-65 The Knapsack Viaduct is a sandstone arch viaduct, designed by John Whitton and built by