The Scottish Naturalist 317 



ice areas were formed by the slowly accumulated rainfalls or 

 snowfalls of repeated years. They originated, as do ice-fields 

 now in Arctic spheres, where 



' ' For ever grows, 

 Amid a region of unmelting snows, 

 A monument — where every flake that falls 

 Gives adamantine firmness to its walls." 



And as they made their profound march across the hills and 

 down the greater valleys, the clouds fulfilled their mission, and 

 the snows renewed the glittering bergs that ocean bore away. 

 This mighty agent moulded itself to every undulation of the 

 land, and yet it glided on. Its foot was heavy, and its will 

 supreme. Rough ways were made smooth : the ice tore off 

 projecting masses and made of them tools, and the most un- 

 yielding rocks were sculptured in a style peculiar to that icy 

 hand. Huge grooves, and delicate lines, and polished surfaces 

 everywhere abound, in evidence of the ice's handiwork. More- 

 over, the tools that the glaciers used are scattered over the 

 country (also sculptured as described), lying upon, or mixed 

 with, immense patches of the chippings and grindings from this 

 great labour. Many attempts have been made to explain the 

 existence of this intense cold, but all the hypotheses are giving 

 way before the noble diction of Astronomy. This " precession of 

 the Equinoxes " doubtless is the sounding line of these climatic 

 changes. The increase of cold was not suddenly brought 

 about : the Pliocene period is the shadow of the coming event, 

 leading on to glacial times, as the autumn leads to winter. Nor 

 was the glacial period one unbroken epoch of ungenerous 

 rigour. It doubtless lasted long, very long ; but there were 

 genial intervals, and these not of short duration, when the vege- 

 tation slowly renewed its reign upon our soil, when the animals 

 retraced their steps into the northern regions (Britain probably 

 was not then an island), and even the neolithic man returned 

 to scenes from whence the ice had driven him. Nor is this the 

 extent of change that then took place. The land sank down 

 beneath the sea till the Atlantic rolled among an Archipelago 

 of ice, whence the bergs broke loose to drop the stolen portions 

 of the land w r herever they might go. This Arctic Ocean reached 

 at its highest considerably above 2,000 feet. How' long it 

 remained at this elevation it is impossible to say ; certainly it 

 did subside, not suddenly, but by halting stages. In Ireland 

 four distinct resting heights have been pretty decidedly made 



