Northern Sea had a connection with the Ponto-Caspian Sea--a sea formed by the junction of the Black Sea and the Caspian (Fig. 12, p. 156). There is geological evidence, as will be explained in the following chapter, that the area of these two seas was considerably larger in glacial times than it is now, and that they were joined across the valley of the Manytch. After the inter-glacial phase of the Glacial period, the North European Ocean became connected with the Atlantic Ocean across the north of England (Fig. 6, p. 126), the junction between the former and the Ponto-Caspian having meanwhile become dry land (Fig. 13, p. 170). A fresh current, now flowing westward, was set up in the North European Ocean, which accounts for the fact just cited that the erratics in the upper continental boulder-clay have travelled in a different direction from those in the lower. The boulder-clay laid down by the sea on the midland and northern counties of England, just as was the case with the similar deposit on the Continent, is generally accredited to the action of land-ice. It is by most geologists looked upon as the ground-moraine, partly of the huge Scandinavian glacier which is supposed to have impinged upon the English coast, partly of local British glaciers. But renewed geological investigations on this point throw doubts upon these theories. Thus Mr. Harmer remarks in a recent contribution to glacial literature (p. 775), that "it is difficult to see how the Baltic glacier could have reached East Anglia, though ice-floes with Scandinavian boulders might easily have done so, while had the Norwegian ice filled the North Sea and overflowed the county of Norfolk, some evidence of its presence ought to be found in the glacial beds of Holland."