34 THE JEANNETTE ARCTIC EXPEDITION. 



he was within three miles of Herald Island, and on the llth 

 of September he was within twenty-five miles of Wrangel 

 Land ; but even these positions were only attained after 

 steaming long distances through labyrinthian lanes, and 

 coming in contact with large bodies of floating ice. 



The Corwin sailed hither and thither, across the open por- 

 tions of the Arctic basin, and much interesting information 

 relating to the native tribes, natural history, and geology of 

 the region was gathered ; but no trace of the Jeannette or 

 missing whalers was found, and at the close of the Arctic 

 summer the Corwin returned to San Francisco. 



The following extracts are from Captain Hooper's account 

 of his voyage : 



"In that part of the Arctic visited by the Corwin the ice 

 is quite different from the ice in the vicinity of Greenland. 

 No immense icebergs raise their frozen peaks hundreds of 

 feet in the air. The highest ice seen by us during the sea- 

 son would not exceed fifty feet in height. The average 

 height of the main pack is from ten to fifteen feet, with 

 hummocks that rise twenty or thirty feet. The specific 

 gravity of sea ice is 91 ; hence only about a tenth is visible 

 above the surface of the water. A field of twenty feet in 

 height may have a depth of nearly two hundred feet. This 

 enormous^ thickness is caused by one layer of ice being 

 forced upon another by the action of wind and current. The 

 greatest thickness it attains by freezing is about eighteen 

 feet. At that depth ice ceases to be a conductor of tem- 

 perature. 



"Along the edge of the pack, during the summer, is gen- 

 erally found a belt of drift ice varying in width according to 

 the direction of the wind. When the wind blows off the 

 pack, drift ice is frequently found fifteen or twenty miles 

 from the main body. At times the pack itself opens in 

 leads, by which it may be penetrated for several miles. In 

 venturing within the limits of the pack, however, a sharp 

 watch must be kept on the movements of the ice, and a re- 

 treat made at the first indication of its closing. 



