The coast-line from Aberlady to Dunbar presents a singular instance of volcanic action. I shall confine myself to the rocks of North Berwick as displayed in excellent sections along the beach. After passing the sandy tract to the west of the town, forming the West Links, we have a perpetual succession of igneous rocks of various descriptions. At the harbour we find a promontory of greenstone, slightly amygdaloidal; proceeding eastwards, similar promontories of the same igneous rock form the Leithies and Leckmoram Ness; whilst, out at sea, the islets of the Lamb and Craigleith and the celebrated Bass Rock are all composed of it. Here, then, we discover evidence of lava flows of the most extensive nature having occurred along this coast-line. An even more interesting feature, perhaps, is found in the enormous deposits of volcanic ash or scoriae which either stretch over the shore in beds, or rise towering above it in sea-cliffs of from 40 to 100 feet in height. To the east of the harbour a bed of red ash occurs; farther east, the colour changes to green. In both cases intercalated layers of sandstone are found within the ash. The ash itself in these beds consists of a heterogeneous mass of small fragments of the rocks of the district—sandstones, limestones, felstones, &c., and forms a compact, asphalt-like deposit, with occasional marks of stratification, yet not so distinct as in the ash-beds farther to the east. Several questions arise as to these great beds of scoriae. First,