On the Glaciated Summit of Alter muir, Pentlands. 311 



outwards to tlie sea on all sides of Scotland. The centre of 

 dispersion in Scotland would, of course, be the highest parts 

 of it — the group of its highest hills, the Grampians, and the 

 high land surrounding them. There the snowfall then, as the 

 rainfall now, would be greatest ; and as the snow accumulated 

 and became, as its habit is under pressure, glacier-ice, it would 

 flow outwards on every side towards the lowest levels it 

 could find. On the western side, the slope being short and 

 steep, it would speedily reach the sea, but on this, the 

 eastern side, the slope being low and long and the country 

 wide, the greatest outspread of ice would necessarily occur. 

 At first, in the beginning of the glacial period, the ice sheet 

 would not be very thick, but as the glacial conditions became 

 more intense, the greater quantity of snow that fell in the 

 longer winters would have less heat to melt it, as well as less 

 time to be melted in the shorter summers, and the ice would 

 grow thicker and thicker, and flow farther and farther out- 

 wards, year by year, till it not only spread over all the low 

 grounds, but even invaded the North Sea, till its advance was 

 checked by the stream of Scandinavian ice coming from the 

 other side as already explained. The obvious result of such 

 a check would be to cause the ice streaming out from Scot- 

 land to be banked upon it, till it swallowed up and overrode, 

 first all the low^er, and finally all the higher hills, on the 

 eastern slope. 



Such seemed to us the only method by which we could 

 suppose the top of AUermuir to have been glaciated, and the 

 stony clay to have been deposited in the little hollow on its 

 highest point. 



Having reached thus far in our cogitations, we crept up to 

 the summit to look again at the scene around us in the new 

 light we had got upon it. The day was fair and bright. A 

 high and dry north wind was on in full blast, the air in con- 

 sequence was free from mist, and we could see far away on 

 every side. 



On the south we looked into the heart of the Pentlands; 

 great steep hills rose up on every side, with narrow deep 

 hollows between ; in one or two water glimmered bright like 

 silver in the sunshine ; on the sides of all the grey grass of 



