58 Dr. J. Rae on the Transposition of Boulders 



by connecting one with another downwards, become channels of 

 drainage. 



There may be several other requisites for this change of salt 

 ice into fresh, such as temperature raised to the freezing-point, 

 so as to enable the brine to work out the cell-walls into channels 

 or tubes — that is, if my theory has any foundation in fact, which 

 may be easily tested by any expedition passing one or more 

 winters on the Arctic, or by any one living where ice of con- 

 siderable thickness is formed on the sea, such as some parts of 

 Norway. 



All that is required, as soon as the winter has advanced far 

 enough for the purpose, is to cut out a block of sea-ice (taking 

 care not to be near the outflow of any fresh-water stream) about 



3 feet square, remove it from the sea to some convenient posi- 

 tion, test its saltness at the time, and at intervals repeat the 

 testing both on its upper and lower surfaces, and observe the 

 drainage if any. 



The result of the above experiment, even if continued for a 

 long while, may not be satisfactory, because the fresh ice that I 

 have described must have been formed at least twelve months, 

 perhaps eighteen months, before. 



The Transposition of Boulders from below to above the Ice. 



When boulders, small stones, sand, gravel, &c. are found 

 lying on sea-ice, it is very generally supposed that they must 

 have rolled down a steep place or fallen from a cliff, or been 

 deposited by a flow of water from a river or other source. 

 There is, however, another way in which boulders &c. get upon 

 floe-ice, which I have not seen mentioned in any book on this 

 subject. 



During the spring of 1847, at Repulse Bay on the Arctic 

 shores of America, I was surprised to observe, after the thaw 

 commenced, that large boulders (some of them 3 or 4 feet in 

 diameter) began to appear on the surface of the ice ; and after a 

 while, about the month of July, they were wholly exposed, 

 whilst the ice below them was strong, firm, and something like 



4 feet thick. 



There were no cliffs or steep banks near from which these 

 boulders could have come ; and the only way in which I could 

 account for their appearance, was that which by subsequent 

 observation I found to be correct. 



On the shores of Repulse Bay the rise and fall of the tide 

 are 6 or 8 feet, sometimes more. When the ice is forming in 

 early winter, it rests, when the tide is out, on any boulders &c. 

 that may be at or near low-water mark. At first, whilst the 



