1873.] WARD — LAKE-DISTKICT GEACIATION. 433 



Fig. 5. — Contour-map, showing the form of the land at 2000 feet. 





VII. Axioms to be bokne in mind in dbawinq Conclusions. 



In drawing conclusions from all that has now been brought for- 

 ward, I would wish to bear in mind the following axioms : — 



1. That a great series of glacial scratches, all pointing in the 

 same direction, evidences the onward movement of a sheet of land- 

 ice, and is not likely to be due to drifting and floating ice. 



2. That the height to which such uniform scratches extend upon 

 the summits of mountains is an index of the amount of hill-area 

 covered by the ice-sheet ; and that the height to which they extend 

 upon the sides of valleys is an index of the least thickness of the ice 

 in such valleys. 



3. That the onward motion in one constant direction of a great 

 thickness of land-ice would tend to push and carry forward portions 

 of the underlying and surrounding rocks in the same direction. 



4. That floating ice might bear boulders in directions in which 

 land-ice could not have transported them. 



5. This being the case, it is evident that boulders from very dif- 

 ferent regions may be commingled, one set being pushed forward 

 by land-ice from one direction, and another set being floated, at a 

 different time, from quite another direction. 



6. Since changes in geography affect ocean-currents, boulders 

 may be floated at one stage of submergence in one direction, and at 

 another stage of submergence in some other direction, thus, again, 

 causing boulders from distinct regions to be commingled at the same 

 spot. 



7. That where a body of land-ice is confined within the narrow- 

 est limits, there, if anywhere, will it be most likely to be pushed 

 over the enclosing walls on one side or the other. 



8. That, in such a case, the push will be given from that direction 



