A visitor to the site has provided some additional information on the old railway seen in
J3626 : Disused Mourne quarry railway (1of4).
“The railway was a 3ft gauge incline railway working on the three-rail principle. Laden wagons descending provided the force to haul the empties up the steep slope.
The centre rail was common to both and at half way or passing places the rails opened out to form two independent passing loops (similar to those on a conventional single-track railway), each with their own rails. After the wagons had crossed they resumed the journey using the common middle rail.
Some inclines were double track but it was usual, over longer distances, to operate on the three rail principle.
The “locomotive” was normally a big wooden drum sited in a building (usually roofed over the drum). The “driver” stood on the edge of the descent for a better view. He operated a hand brake on the drum to control the speed of decent.
The rope (or wire) was attached to one or more wagons at a length that allowed the wagons to pass at the loop. Normally the wagons were attached to the rope with a sprag (a one-way freewheel clutch). The rope was endless and was marked showing where sprags were to be fitted.
Without sprags the ascending and descending wagons would collide. On long inclines (and this is one of the longest I have ever seen) there would be an escape into a pit (drag) so that if the rope broke or the load ran away a catch point could be operated to derail the wagon”.