APPENDIX 733 



as New York or London to any point within the northern hemisphere, 

 and for such undertakings this map will have no significance. 



FACTORS MODIFYING THE THEORETICAL RESULTS 



Should anyone desire to use this map as the basis either for the 

 planning of an actual polar expedition or for the illustration of theories 

 upon the subject, he will have to bear in mind various modifying fac- 

 tors, the most important of which are the following. 



1. When traveling over the surface of the mobile north-polar ice the 

 first difficulty is with currents. For instance, it is possible to sail com- 

 paratively near the North Pole in the longitude of Spitsbergen; but 

 Peary and most of his followers found that when they strove to march 

 north in this region their efforts were in part cancelled by the continuous 

 southward drift of the ice over which they were traveling. Our own 

 work has shown that a similar southward drift, although perhaps not so 

 strong a one, would have to be faced by anyone traveling north near the 

 138th meridian W. To the north of Grant Land Peary found an east- 

 ward drift though it did not handicap him materially. It is probable, 

 on the other hand, that anyone starting north from Wrangel Island or 

 the New Siberia Islands would get considerable help from a current 

 running partly in his favor. 



2. At times an even more serious handicap than an adverse current 

 is the frequency of open leads. Judging from the narratives of polar 

 explorers, this particular handicap is most serious in the region north of 

 eastern Siberia, where Baron Wrangel traveled a century ago, and in the 

 belt of generally similar conditions north of Alaska with which I have 

 personal acquaintance. This handicap is of little weight northwest of 

 Prince Patrick Island, as I have found by experience, and northwest 

 of Cape Thomas Hubbard and north of Cape Columbia, as shown by 

 the narratives of Peary and MacMillan. 



3. In regions where currents are violent the ice is broken up with a 

 resulting formation not only of the leads of open water which we have 

 considered, but the heavy pressure ridges which make sledge travel more 

 arduous and occasionally compel actual road making with pickaxes. The 

 trouble with pressure ridges is generally greatest near land and becomes 

 less and less as one goes farther from shore. They are the more trouble- 

 some the younger the ice. It seems now fairly clear that much of the 

 polar ice is formed originally on the American and Siberian side of the 

 Arctic and drifts across past the northern end of Greenland towards 

 Franz Josef Land where it vanishes in the Gulf Stream. 



This is one of the many reasons which made Peary's "American route 

 to the Pole" the most desirable. Not only could he sail farther north by 

 ship and then have comparatively few leads to contend with, but he had 

 the added advantage of traveling in considerable part over ice which 

 had been formed many years earlier, perhaps in the Beaufort Sea, and 



