In a vastly remote past, and for a vastly extended period, the mighty deep rolled over the surface of a world inform and void, depositing a sediment of its used up living tenants, the microscopic cases of foraminiferæ, sponges, sea-urchins, husks, and the cast limbs of crustaceans. The descending shells of the diatoms like a subaqueous snow gradually buried the larger dejections. This went on till the sediment had attained a thickness of over one thousand feet. Then the earth beneath, heaved and tossed in sleep, cast off its white featherbed, projected it on high to become the chalk formation that occupies so distinct and extended a position in the geological structure of the globe. The chalk may be traced from the North of Ireland to the Crimea, a distance of about 11,140 geographical miles, and, in an opposite direction, from the South of Sweden to Bordeaux, a distance of 840 geographical miles. It extends as a broad belt across France, like the sash of a Republican mayor. You may travel from Calais to Vendôme, to Tours, Poitiers, Angoulême, to the Gironde, and you are on chalk the whole way. It stretches through Central Europe, and is seen in North Africa. From the Crimea it reaches into Syria, and may be traced as far as the shores of the sea of Aral in Central Asia. The chalk is not throughout alike in texture; hard beds alternate with others that are soft--beds with flints like plum-cake, and beds without, like white Spanish bread. We are accustomed in England to chalk in rolling downs, except where bitten into by the sea, but elsewhere it is riven, and presents cliffs, and these cliffs are not at all like that of Shakespeare at Dover, but overhang, where hard beds alternate with others that are friable. These latter are corroded by the weather, and leave the more compact projecting like the roofs of penthouses. They are furrowed horizontally, licked smooth by the wind and rain. Not only so, but the chalk cliffs are riddled with caves, that are ancient water-courses. The rain falling on the surface is drunk by the thirsty soil, and it sinks till, finding where the chalk is tender, it forms a channel and flows as a subterranean rill, spouts forth on the face of the crags, till sinking still lower, it finds an exit at the bottom of the cliff, when it leaves its ancient conduit high and dry.