650 PHYSICAL PROPERTIES OF ICE. 



inducements we were never able to find sea-ice, in situ*, either 

 eatable when solid or drinkable when thawed, it being invariably 

 much too salt. The only exception (if it may be called one) to this 

 rule, was when we found rough ice, which, from its wasted 

 appearance and irregular form, had evidenty been the formation of 

 a previous winter. This old ice, if projecting a foot or two above 

 the water-level, was almost invariably fresh, and, when thawed 

 gave excellent drinking-water. It may be said that these pieces 

 of fresh ice were fragments of glaciers or icebergs ; but this could 

 not be so, as they were found where neither glaciers nor icebergs 

 are ever seen. 



How is this to be accounted for ? Unfortunately I have only a 

 theory to offer in explanation. 



When the sea freezes by the abstraction of heat from its surface 

 I do not think that the saline matter, although retained in and 

 incorporated with the ice, assumes the solid state, unless the cold is 

 very intense, but that it remains fluid in the form of a very strong 

 brine enclosed in very minute cells. So long as the ice continues 

 to float at the same level, or nearly the same level, as the sea, this 

 brine remains ; but when the ice is raised a little above the water- 

 level, the brine by its greater s])ecific gravity, and probably by 

 some solvent quality acting on the ice, gradually drains off from 

 the ice so raised ; and the small cells, 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 wo7'k 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 anyone living where ice of considerable 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 position, 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, mai/ not be satisfactory, because the fresh ice, that I have 

 described must have been formed at least 12 months, perhaps 

 18 months, before. 



The Transposition of Boulders from beloiv 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. 



* What I mean by ice in situ is ice lying flat and unbroken on the sea, as 

 formed during the winter it is formed in. 



