DBUMLUSTS. 297 



pressure of the water would be too great for any living thing 

 to endure. Yet many delicate organisms have been dredged 

 up from depths at which the pressure must certainly be no 

 trifle. Now, there seems to be just as little difficulty in believ- 

 ing that these organisms existed in a perfect state at the bot- 

 tom of the ocean, as that shells imbedded in clay would remain 

 unbroken underneath the pressure of a superincumbent ice- 

 sheet of equal or greater weight. If the ice were in motion, 

 the clay with its included shells might be plowed out bodily, 

 or be merely crumpled and contorted ; or it might be ridden 

 over with little or no disturbance ; or, on the other hand, it 

 might become involved with subglacial debris, and be kneaded 

 up and rolled forward — the shells in this case being broken, 

 crushed, and striated, just as we find that the shells in certain 

 areas of till have been. The fate of the fossiliferous beds 

 would, in short, be determined by the rate of flow and degree 

 of pressure exerted by the superincumbent quasi- viscous body 

 — the motion of which would be largely controlled b} r the 

 physical features of the ground across which it crept. 



