The Drift or Boulder Formation, 335 



this theory would not account for the drift of America, he sup- 

 poses a second displacement, whereby the pole was removed to 

 the vicinity of the City of Boston, in the United States. Great 

 quantities of ice and snow accumulated in Europe and America 

 during these periods, which on the return of the pole to its present 

 position melted, occasioning great floods, which dispersed the 

 boulders and spread the drift over the land. The theory which 

 has received the greatest amount of respect is that which attri- 

 butes the drift to vast glacier.^ that covered a large portion of the 

 Arctic and North temperate regions, and by tlieir continual flow 

 towards the south, shoved along or otherwise transported the 

 boulders and debris of which the drift is composed. This theory 

 was suggested by observations made among the Alps, where, in 

 those mountains covered with perpetual snow, the ravines that 

 descend their sides are full of ice, which moves or rather flows 

 down — for this glacier ice is not solid, but in a viscid state — with 

 exceeding slowness, bearing upon its surface or embedded in it 

 masses of rock of all sizes, which it deposits on the plains below. 

 These glaciers polish the solid rocks over which they pass in a 

 ^ manner similar to the polishing and grooving referred to in the 

 drift of this and other countries. This theory has for its suppor- 

 ters some of the most distinguished philosophers of the age, among 

 whom may be mentioned Professor Agassiz. It is called the 

 Glacial Theory, and supposes a period of extreme cold, durin<r 

 which the Antarctic climate was experienced so far south as the 

 present United States. 



The " Iceberg Theory," much advocated by Sir Charles Lyell, 

 has also many very eminent men for its supporters. According 

 to this view, during the period of the drift, the northern portions 

 of the present continents of Europe and America were submero-ed 

 beneath the ocean, but to no great depth, and the boulders were 

 transported by icebergs floating from the north towards the 

 south. These bergs in their course rubbed along the bottom, and 

 while they polished the rock surfaces, the stones imbedded in the 

 ice occasioned the long parallel grooves anj scratches which may- 

 be seen wherever the drift is removed. That the icebero-s of the 

 present day do carry boulders, gravel, sand and clay, which have 

 become attached to them while in contact with the northern sea 

 coasts, is a well established fact. Their course in the Atlantic is 

 always towards the south, and when they enter the warm climates 

 of the sea, they melt away, and drop tbe boulders and other mate- 



