PHYSICAL AND CLIMATAL CONDITIONS. 101 



question by ascertaining the deposition of marine boulder- 

 clay, or at least of a deposit of sand and clay, with 

 fragments of various rocks over areas perhaps as great as 

 those now covered with similar deposits in the northern 

 hemisphere. It is most instructive to find that a bed of 

 this stony mud is in process of deposition from floating 

 ice in the southern ocean, and this with such rapidity, 

 that the foraminifera and other organisms elsewhere 

 forming the deep-sea ooze are quite masked by it, while 

 it is also possible that in some places all traces of these 

 may be dissolved out by carbonic acid. It is further 

 interesting to find such deposition taking place so exten- 

 sively under conditions probably much less favourable 

 than those which prevailed in Europe and America 

 during the great Pleistocene subsidence. 



These facts fully confirm the conclusions stated above 

 with reference to the boulder-clay or till of North 

 America, and whicli I have endeavoured to establish by 

 the nature of the deposits now forming in the areas of 

 ice-drift of the American coast, by the distribution and 

 chemical condition of the boulder-clay itself, and by the 

 occurrence of marine organisms in it. It is to be hoped 

 that in future we shall not have so confident assertion 

 that these remarkable clays are due to the direct action 

 of land ice on the surface of our continents. 



If the bottom of the South Pacific and Antarctic 

 oceans could be elevated into land, we should see the 

 evidence of glacier action on the hills representing the 

 islands now out of water and extending from these a vast 

 area of boulder-clay reaching as far north as our similar 

 records of the Pleistocene submergence spread to the 

 south, and probably holding in many places marine 

 organic remains, though there might be expected to be 



