 By contrast, the Lithgow Zig Zag railway, built between 1866 and 1869, required much heavier engineering, including four large rock cuttings, three fine stone viaducts with semi-circular arches (originally four were planned, but one was built as an embankment instead) and a short tunnel (three tunnels were planned, but two were daylighted during construction due to leaks, becoming two of the four cuttings mentioned above).In the descent of the middle road, the line dropped between the reversing points, being part of the descent from Clarence.The whole route had a ruling grade of 1