A rail consultant has told of his surprise at finding a Victorian engineer's proposals for a rail link between Scotland and Ireland.
Edinburgh-based David Spaven believed the plans for a tunnel, causeway or an undersea bridge between Stranraer and Belfast were not widely known today.
The plans feature in a new book, Mapping the Railways, Mr Spaven has co-written with author Julian Holland.
It also includes abandoned ideas for light railways on Skye and Lewis.
Published for the The Times by Collins, the book has been described as the most comprehensive collection of British railway maps dating from 1819 to the present day.
Mr Spaven worked as a British Rail manager for 18 years until 1995.
He stood as a Green Party candidate in Glasgow Maryhill in 1987 and was the first chairman of transport campaign group Transform Scotland, and has also been involved with congestion charge support group Get Edinburgh Moving.
The book is his latest collaboration with Mr Holland, a railway writer and photographer.
Much of the Scottish material was drawn from maps held by the National Library of Scotland in Edinburgh.
The undersea rail link, proposed by engineer Luke Livingston Macassey, came to light during Mr Spaven's research of Victorian-era railway maps and plans.
He said: "The book has been a fantastic journey of discovery for me.
"One of the big surprises was a prospectus for a tunnel under the North Channel between Stranraer and Belfast.
"At first I thought it was a Victorian spoof, but through more research I found the person behind the idea was a competent and well regarded engineer."
According to Mapping the Railways, the proposals published in 1890 were for a rail link using either a tunnel, a submerged "tubular bridge" or a solid causeway.
The engineer said the rail connection would quicken travel between Scotland and Ireland and would also spare people "the horrors of 20 miles in rough seas".
Mr Spaven said few people were also likely be aware of plans to build light, narrow gauge railways on Lewis, in the Western Isles, and on Skye.
A map from 1919 shows a proposed line from Ardvasar in the south of Skye to Dunvegan in the north of the island.
A light railway network connecting Carloway, Ness and Stornoway on Lewis is also marked on the map.
Mr Spaven said: "There was a short window of opportunity for these railways to be built.
"After the First World War lorries were more readily available and that closed the window on the light railways."