At the close of the period the land here sank beneath the sea--again a sea of coral islands like the South Pacific of to-day. There were many oscillations of level, or changes of currents; and bands of clay, when mud from the land was laid down, alternate with beds of limestone formed in the clearer coral seas. These strata form a period known as the Jurassic, from the large development of the rocks in the Jura mountains. In England the period includes the Liassic and Oolitic epochs. The Liassic strata stretch across England from Lyme Regis in Dorset to Whitby in Yorkshire. Most of the strata we are describing run across England from south-west to north-east. After they were laid down a movement of elevation, connected with the movement which raised the Alps in Europe, took place along the lines of the Welsh and Scotch mountains and the chain of Scandinavia, which raised the various strata, and left them dipping to the south-east. Worn down by denudation the edges are now exposed in lines running south-west to north-east, while the strata dip south-east under the edges of the more recent strata. The Lias is noted for its ammonites, and especially for its great marine reptiles, Ichthyosaurus and Plesiosaurus. The Oolitic Epoch follows--a long period during which the fine limestone, the Bath freestone, was made; the limestones of the Cotswolds, beds of clay known as the Oxford and Kimmeridge clays; and again coral reefs left the rock known as coral rag. In the later part of the period were formed the Portland and Purbeck beds, marine and freshwater limestones, which contain also an old land surface, which has left silicified trunks of trees and stems of cycads. And now following on these came our Wealden strata, the beginning of the Cretaceous period. You see what ages and ages had gone before, and that when Wealden times came, far back as they are, the world's history was comparatively approaching modern times. We must remember that all these formations, of which we have given a rapid sketch, are of great thickness,--thousands of feet of rock,--and represent vast ages of time. See what we have got to from looking at the shells in the sea cliff! We have come to learn something of the world's old history. We have been carried back through ages that pass our imagination to the world's beginning, to the time of the molten globe, before ever it was cool enough to allow life--we know not how--to begin upon its surface. And Astronomy will take us back into an even more distant past, and show us a nebulous mist of vast extent stretching out into space like the nebulae observed in the heavens to-day, before sun and planets and moons were yet formed. So we are carried into the infinite of time and space, and questions arise beyond the power of human mind to solve.