Keywords: Break up length with centres (Walker 1888).jpg Break up length with centres Severn Tunnel construction Original Thomas A Walker 1888 The Severn Tunnel Facing page 84 <br>Scan Internet Archive http //www archive org/details/severntunnelits01walkgoog 1888 Thomas A Walker PD-old-100 Scans from Walker 1888 the Severn Tunnel Tunnelling |