1875 THICKNESS OF ICE. 79 



ice of a similar description had frequently been met 

 with, it was popularly supposed that it was formed only 

 in protected bays which seldom cleared out. One 

 Arctic authority asked me to endeavour to place it 

 beyond a doubt whether it were possible for salt-water 

 ice to attain more than a mean thickness of seven feet ; 

 and Dr. Hayes, one of the latest explorers and an un- 

 doubted authority, was of opinion that ice soon reaches 

 its maximum thickness by direct freezing ; he states, 

 indeed, that he had never seen an ice-table formed by 

 direct freezing that exceeded eighteen feet in thickness. 

 I was, therefore, naturally astonished to see such large 

 quantities of heavy ice. 



Now that we know that the ice in the Polar Sea is 

 upwards of eighty and one hundred feet thick, it may 

 be as well to draw attention to the reports of former 

 navigators on this subject. Scoresby describes the ice 

 met with in the Spitsbergen seas as ' consisting of a 

 single sheet of ice, having its surface raised four or six 

 feet above the level of the water, and its base depressed 

 to the depth of ten to twenty feet beneath,' thus mak- 

 ing it twenty-six feet in thickness. Sir Edward Parry, 

 in 1820, when he had advanced to the westward of 

 Cape Hay in Melville Island, and was in fact at the 

 entrance to the Polar Sea, remarks with astonishment 

 on the thickness of a piece of a regular floe, wdiich 

 when measured by Captain Beechey was found to be 

 forty-two feet. 



Sir Eobert M'Clure reports the ice off the mouth of 

 the Mackenzie River and on the west coast of Banks 

 Land as drawing from forty to fifty feet water, and 

 sometimes even seventy- eight feet. All the voyagers to 



