152 MAN AND THE GLACIAL PERIOD. 



many features of association, condition, and position in- 

 consistent with, what we should be led to expect from a 

 study of recent marine life, that conchologists are unani- 

 mous in declaring that not one single group of them is on 

 the site whereon the shells lived. It is a most significant 

 fact — one out of a hundred which could be cited did space 

 permit — that in the ten thousand square miles of, as it is 

 supposed, recently elevated sea-bottom, not a single ex- 

 ample of a bivalve shell with its valves in apposition has 

 ever been found ! Nor has a boulder or other stone been 

 found encrusted with those ubiquitous marine parasites, 

 the barnacles. 



" The evidences of the action of land-ice within the area 

 are everywhere apparent in the constancy of direction of — 

 (1.) Striae upon rock surfaces. (2.) The terminal curva- 

 ture of rocks. (3.) The ' pull-over ' of soft rocks. (4.) 

 The transportal of local boulders. (5.) The orientation of 

 the long axes of large boulders. (6.) The false bedding 

 of sands and gravels. (7.) The elongation of drift-hills. 

 (8.) The relations of ' crag and tail.' There is a similar 

 general constancy, too, in the directions of the striae upon 

 large boulders. Upon the under side they run longitudi- 

 nally from southeast (or thereabouts) to northwest, while 

 upon the upper surface they originate at the opposite 

 end, showing that the scratches on the under side were 

 produced by the stone being dragged from northwest to 

 southeast, while those on the top were the product of 

 the passage of stone-laden ice over it in the same direc- 

 tion. 



" Such an agreement cannot be fortuitous, but must be 

 attributed to the operation of some agent acting in close 

 parallelism over the whole area. To attribute such regu- 

 larity to the action of marine currents is to ignore the 

 most elementary principles of marine hydrology. Ice- 

 bergs must, in the nature of things, be the most erratic 

 of all agents, for the direction of drift is determined — 



