Icebergs upon Drift. 449 



many lialf black, apparently, with earth from the land to 

 which they had adhered, or with mud from the bottom on 

 which thev had formed. 



Dr. Mertens, in his memoir upon the glaciers of Spitzber- 

 gen, said that his colleague, Mr. E. Hobart, had seen floating 

 ice in crossing Bell Sound, stained at the surface with earth, 

 which, for the moment, was taken for islands. 



The negative testimony upon this subject will, to many, 

 appear remarkable ; for, of more than sixty persons whom I 

 have examined, only seven remember to have seen foreign 

 materials upon the iceberg. Captain Crocker, who, as I have 

 before remarked, has crossed the Atlantic one hundred and 

 sixty-four times, and who says that he has seen thousands of 

 icebergs, never remembers to have witnessed any such appear- 

 ance. Captain Luce, who had seen hundreds of icebergs, 

 never saw any stones or earth upon them. ]Mr. Fernald, a re- 

 markably accurate observer, although he says that he has seen 

 hundreds of icebergs between Georgia and Sandwich Land, 

 never saw stones or earth on any of them afloat. The com- 

 mander of the French Exploring Expedition makes no mention 

 of his having seen extraneous matters on the numerous islands 

 seen by him, although he had been particularly instructed to 

 notice such phenomena. Dr. Mertens says that, in the voy- 

 ages of the R.!^cherche, in the Spitzbergen seas, he never saw 

 blocks transported by ice. Captain Biscoe, who had extended 

 his researches in the Antarctic, says, in a letter to Mr. Darwin, 

 that he had never observed, in a single instance, mud or 

 fragments of stone on the numerous icebergs encountered by 

 him in his voyage. The evidence upon tliis subject has con- 

 vinced me that islands of ice, floating at a distance from their 

 source, are remarkably free from all impurities. 



It must be remembered that the evidence upon this subject 

 is negative, and not entitled to the same weight as positive 

 testimony. The voyagers are so much occupied with the 

 perils of navigation among the ice as to be inattentive to 

 phenomena whicli would be observed by scientific men. 

 Again, where mud or stones were attached to the bottom of 



50 



