EXPEDITION TOWARD THE NORTH POLE. 387 



extended beyond its j)resent limits, and step by step its greater exten- 

 sion may be traced down to Meyringen, and, in connection with other 

 glaciers from other valleys of the Bernese Oberland, it may be tracked 

 as far as Thnn or Berne, when the relation to the Alps becomes compli- 

 cated with features indicating that the whole valley of Switzerland, 

 between the Alps and the Jura, was once occupied by ice. On the other 

 hand, there are evident signs of the former presence of local glaciers in 

 the Jura, as, for instance, on the Dent de Vaulion, which mark a later 

 era in the history of glaciation in Switzerland. Now the traces ol the 

 former existence of extensive sheets of ice over the continent of [North 

 America are everywhere most plainly seen, but no one has yet under- 

 taken to determine in what relation these glaciated surfaces of past ages 

 stand to the ice-fields of the present day in the Arctics. The scieutitic 

 men connected with Captain Hall's expedition would render science an 

 important service if they could notice the trend and bearing of all the 

 glacial scratches they may observe upon denudated surfaces wherever 

 they land. It would be advisable for them, if possible, to break off 

 fragments of such glaciated rocks and mark with an arrow their bear- 

 ing. It would be equally important to notice how far the loose materials, 

 j)ebbles, bowlders, &c., differ in their miueralogical character from the 

 surface on which they re^^t, and to what extent they are themselves 

 polished, rounded, scratched, or furrowed, and also what is the nature 

 of the clay or sand which holds them together. It would be, particularly 

 interesting to learn how far there are angular bowlders among these 

 loose materials, and what is their position with reference to the com- 

 pacted drift made up of rounded, polished, and scratched pebbles and 

 bowlders. Should an opportunity occur of tracing the loose materials 

 of any locality to some rock in situ, at a greater or less distance, and 

 the nature of the materials should leave no doubt of their identity, this 

 would afford an invaluable iiulication of the direction in which the loose 

 materials have traveled. Any indication relating to the differences of 

 level among such materials would add to the value of the observation. 

 I have purposely avoided all theoreHcal considerations, and only called 

 attention to the fiicts which it is most important to ascertain, in order 

 to have a statement as unbiased as possible. 



L. Agassiz. 



