most pronounced character have been brought about solely by the action of glaciers. In the case of the erratics and morainic accumulations of the basin of the Rhone, the action of icebergs is entirely precluded. I may now mention some of the more remarkable examples of intercrossings of erratics which have been recorded from the glacial accumulations of north Germany, etc. An examination of the glacial striæ, _roches moutonnées_, and boulder-clays of Saxony leads to the conviction, according to Credner, Penck, Torell, Helland, and others, that the whole of that region has been invaded by the great Scandinavian _mer de glace_ which flowed into Saxony from NNE. to SSW. Erratics from southern Sweden and Gothland occur in the boulder-clay, and the presence of these, taken in connection with the direction of the glaciation, leaves us no alternative but to agree with the conclusions arrived at by the Saxon geologists. But, apparently in direct contradiction of this conclusion, we have evidence to show that boulders of the same kinds of rock occur in Denmark and Holland, pointing to a former ice-flow from north-east to south-west and west. Thus boulders derived from Gothland occur at Gröningen in Holland, while fragments from the island of Öland are met with in Faxö; and erratics from the borders of the Gulf of Finland are encountered at Hamburg. Indeed, when geologists come to examine the erratics in north Germany and Poland generally, they find evidence of apparently two ice-flows--one of which went south-south-west, south, and south-east--spreading out, as it were, in a fan-shape towards the southern limits reached by the great "Northern Drift,"--while the other seems to have followed the course of the Baltic depression, overflowing the low-grounds of northern Prussia, Holland, etc., in a south-west and west direction. Now, it is quite evident that no one _mer de glace_ could have followed these various directions at one and the same time. The explanation of the apparent anomaly, however, is not far to seek. It is reasonable to infer that long before the _mer de glace_ had attained its maximum dimensions, when as yet it was confined to the basin of the Baltic and was only able to overflow the northern regions of Prussia, etc., its course would be determined by the contour of the pavement upon which it advanced. It would, therefore, be compelled to follow the Baltic depression, and for a long time it would carry erratics from Finland, the Baltic islands, and eastern Sweden in a south-west and west-south-west direction. And this would continue to be the direction even after a considerable portion of the low-grounds of Prussia, etc., had been overflowed. But when the ice-sheet was enabled to advance south into Saxony, Poland, and Lithuania, erratics from Finland, the Baltic islands, etc., would necessarily cease to travel towards the west, and hold on a south-south-east, south, and south-south-west course. Again, when the _mer de glace_ was on the