Page:Quarterly Journal of the Geological Society of London, vol. 29.djvu/271

 glacial period. But if one half of the world was so covered, the other half cannot have escaped. The change in climate which produced this period of intense cold is theoretically accounted for by astronomical facts.

The whole theory was based upon many sets of observed facts which combine severally and in groups, and lead gradually from smaller to greater conclusions as the number of facts observed grows.

My observations made this year in Ireland, combined with the rest of my facts, have led me from small mountain-glaciers to a sheet more than 2000 feet thick, covering the northern half of Ireland. I have got a long way towards the most advanced glacial theory since I printed ' Frost and lire,' in 1865 ; but I cannot yet see my way to a universal ice-crust. Wbat would become of vegetation and animal life if the uppermost geological formation were everywhere frozen water ? That being the advanced theory, and one difficulty, let me add more facts to my budget, and look at the other half of Ireland, with the most advanced glacial theory borne in mind.

8. S. W. Ireland. — Any map of Ireland shows the general shape of the south-western end of the island. The coast-line is that of a series of long sea-loughs. The country is a series of long ridges of high land, with deep grooves between, which trend generally south- westward on the strike. It will be argued that the strike accounts for the shape of the land. I do not think that it does.

The sea ebbs and flows in these grooves, and rivers come down through drift at the ends of the sea- loughs. Knowing something of Irish glaciation, one of these long ridges explains the rest.

The first place examined in 1872 was Bere Haven. There glacial action is conspicuous. Bocks at the sea-level are polished and striated, and Boulder-clay with scratched stones in it rests upon grooved rock in Bere Island. A hot day's wank there showed that ice which did this work came off the ridge from the flanks of the highest hill in sight, " Hungry Hill." It crossed Bere Haven, and went over Bere Island at a height of about 800 feet. It was very heavy ice according to the record. If the ice was at least a thousand feet thick, and moved down from the ridge on one side, as in case 5, it must have done the same on the other. In fact on the other side at Killmakillogue Harbour, and at Derreen House, two large local glaciers met and left their story inscribed in plain lines upon the rock. In the middle of this harbour is " Spanish Island." It is a pile of large glaciated rolled stones arranged in a crescent-form, with a small patch of scarped Boulder-clay ten feet high and a few yards wide left standing by the sea.

On this patch grass grows ; and all the stones in the clay are finely glaciated. The north-eastern horn of this harbour is the scarped end of a long hill of Boulder-clay of the same kind, on which is a good farm, running parallel to the long arm of the sea which is called Kenmare river ; and ridges like it are features in the landscape on both sides of the lough for many miles. To an eye used to look for