THE GLACIAL PERIOD. 171 



they had long excited wonder before any serious attempt was 

 made to account for them in a natural way. Numerous are the 

 myths and legends connected with the great boulders of our 

 own country. They are the "giant's putting-stones," the 

 "deil's burdens," the "witch's hearth -stones," of the fanciful 

 peasantry. Zealous antiquaries have occasionally claimed them 

 as monuments set up by man in some long-forgotten age. In 

 later times they have been ascribed by serious observers, 

 amongst others by Deluc, to the underground forces of nature — 

 the shattered fragments resulting from the explosion of im- 

 prisoned gas. Others again have attributed them to the action 

 of sudden torrential floods, pouring in vast volumes down 

 mountain -valleys to the low grounds — a view which was 

 speedily abandoned when the distances which the boulders 

 must have travelled came to be better known. The enormous 

 size attained by many of the blocks was also a difficulty which 

 this hypothesis could not remove. It was found, for example, 

 that some of the great boulders lying upon the slopes of the 

 Jura, and which had come from the upper reaches of the 

 Ehone valley, measured upwards of 10,000 cubic feet. The 

 famous Pierre a Bot, above the Lake Neuchatel, is a block of 

 granite estimated to weigh 1500 tons. It is needless to say 

 that there is no river which could possibly move masses so 

 enormous as these. The very general distribution of erratic 

 blocks by and by suggested another explanation of their origin. 

 They had been traced across nearly the whole breadth of 

 Northern Europe, from Holland to St. Petersburg and Moscow — 

 they swarmed upon the low grounds bordering on the Baltic, — 

 they were hardly less abundant in Middle Germany, they were 

 sprinkled plentifully over Scotland, Ireland, and a large part of 

 England. Their occurrence in the alpine regions of Switzer- 

 land and the Pyrenees was notorious, and they had been 

 observed also as far south as Granada. The general directions 

 in which they had travelled had likewise been ascertained. 

 Thus it was known that many of the large blocks scattered 

 over the surface of Northern Germany had been derived from 



