"All the characteristic evidences of the action of land-ice can be found in the greatest perfection in many parts of England and Wales. Drumlins, kames, _roches moutonnées_, far-travelled erratics, terminal moraines, and perched blocks, all occur. There are, besides, in the wide-spread deposits of boulder-clay which cover so many thousands of square miles on the low grounds lying on either side of the Pennine chain, evidences of the operation of ice-masses of a size far exceeding that of the grandest of existing European glaciers. But, while the proofs of protracted and severe glaciation are thus patent, there are, nevertheless, many apparently anomalous circumstances which arrest the attention when the whole country is surveyed. The glacial phenomena appear to be strictly limited to the country lying to the northward of a line extending from the Bristol Channel to the mouth of the Thames; and within the glaciated area there are many extensive tracts of land devoid of 'drift' or other indications of ice-action. "By comparison with the phenomena displayed in the North American continent, English glacial geology must seem puny and insignificant; but, just as with the features of the 'Solid Geology,' we have compressed within the narrow limits of our isles an epitome of the features which across the Atlantic require a continent for their exposition. It has resulted from this concentration that English geology requires a much closer and more minute investigation. And the difficulty which has been experienced by glacial geologists of dealing with an involved series of facts has, in the absence of any clue leading to the co-ordination of a vast series of more or less disconnected observations, resulted in the adoption, to meet certain local anomalies, of explanations which were very difficult if not impossible of reconciliation with facts observed in adjacent areas. Thus, to account for shell-bearing drift extending up to the water-shed on one side of a lofty range of hills, a submergence of the land to a depth of 1,400 feet has been postulated; leaving for independent explanation the fact, that the opposite slopes of the hills and the low ground beyond were absolutely destitute of drift or of any evidence of marine action. "In the following pages I must adopt a somewhat dogmatic tone, in order to confine myself within the limits of space which are imposed; and trust rather to the cohesion and consistency of the explanations offered and to a few pregnant facts than to the weighing and contrasting of rival theories.