While mapping the area south of Edinburgh, around Penicuik, Bilston, and Loanhead, I was aware of a linear man-made artefact following roughly the course of the A701, both from on the ground surveys and clearly visible on bing imagery
This had been already mapped in 2009 as a disused canal, but a web search brought up no results for a canal in this area, and it was not shown on historical OS mapping, so I was to sure this was correct. Current OS StreetView labels this feature as a Dismantled Railway, and again I did not think this was correct, as no trace of this is shown on historical OS mapping, and there is another railway nearby on a different alignment.
Finally, browsing other historical maps on the National Library of Scotland site , I found a clue, the feature was tagged on the Ordnance Survey Six-inch 1st edition, 1843-1882 map as "Course of Conduit, Edinburgh Water Works", and can be traced back to the nearby Glencorse Reservoir. It can also be traced in the other direction into Edinburgh, where it links up with a couple of other embankment features I had noticed before.
I have mapped the sections of the pipeline that are visible to some extent (by embankment or other feature) although have not connected the whole route up as much of it is covered by more recent development.