As the season for active out of door geological work is now approaching, I propose to give a brief glance at some interesting features of the South Wales coal-field, in the hopes that pedestrian geologists may be tempted to make it one of the scenes of their labours. And they will be richly rewarded; for, though coal-fields generally give us an impression of a black, unsightly country, without vegetation or anything pleasant for the eye to rest upon, they are not all alike, and that of South Wales is as rich in beautiful scenery above ground, as it is in the precious mineral beneath. Glorious hills intersected by narrow valleys and wooded dells, each washed by its mountain-stream, and antiquities—in the shape of castles, abbeys, cromlechs, and cairns, may tempt the tourist to whom geology does not hold out sufficient inducement. It is in outward features, which I shall first touch upon, that this differs so much from other coal-fields, the basin being more clearly marked, and the underlying grits and limestones, being more uniform in their development than in any district in Great Britain.