During a recent visit to the tunnel now in course of construction beneath the Severn, I was taken by my friend Mr. Evan Jones, of University College, to examine a heap of Triassic pebbles and conglomerate, which had been exploited from the bottom of one of the shafts of the tunnel on the Portskewet side of the river. My attention was at once arrested by the striated and polished surfaces presented by many of the pebbles, and the results of the short examination I was able to make of them are embodied in the following note.