Stone Thingy. Conduit. Redmires. A thingy was put on top of the thingy to make it a sighting tower. There is other one on yon end of Stanage. Sighting between the line of them determined the line for the Rivelin Tunnel. Started in 1903 and finished in 6 years later, it runs from Ladybower (near the Fisheries Office) to where the ornate metal gates are on the side of Rivelin Reservoirs. With the exception of the Severn Tunnel, which is only 12 yards longer, it is the longest tunnel in England, and certainly the longest carrying water. The length of the tunnel is 4 miles 612 yards, and the gradient is 1 in 3600. Five per cent more water comes out than goes in, and ways has (on average), which is quite ‘interesting’ when you think that the railway, evacuation, lighting and ventilation for the tunnel was all done by electricity. Some historians / engineers reckon there muat have been >100 volts D.C. around the inside of a very wet 8ft diameter tunnel 😳. The finished lined tunnel is 6.5ft high and 6ft wide.