Slate operations on the Welsh Highland Railway

The original Welsh Highland Railway (WHR) owed its existence to the narrow gauge railways and tramways built to serve commercial slate traffic from slate quarries and other mineral extraction operations along its route. During the first world war as well as slate other materials such as timber were carried by the North Wales Narrow Gauge Railways, the precursor of the northern half of the Welsh Highland Railway, from the Beddgelert Forest extension.

Source: Wikipedia — Slate operations on the Welsh Highland Railway (CC BY-SA 4.0)