18 



way, masses of any size may be formed. The disruptions so> 

 common during the summer months, as also the overlapping 

 of the fields, will likewise lay the foundation for further accu- 

 mulations. The cause assigned by Mr. Lesslie will also assist 

 in accounting for their progressive increase. " The most sa- 

 tisfactory mode," remarks this able philosopher, " of explain- 

 ing the phenomenon, is to refer it to the operation of a general 

 principle, by which the inequalities on the surface of a field 

 of ice must be constantly increased. The lower parts of the 

 field being nearer the tempered mass of the ocean, are not so 

 eold as those which project into the atmosphere, and, conse- 

 quently, the air which ascends, becoming chilled in sweeping 

 over the eminences, there deposits some of its moisture, form- 

 ing an icy coat. But this continued incrustation, in the lapse 

 of ages, produces a vast accumulation, till the shapeless mass 

 is at length precipitated by its own weight." 



With regard to the kind of solution which the field-ice 

 affords, a variety of opinions have prevailed. Some asserting 

 that the solution had a saline taste, others, that it was quite 

 free from it. This discordancy may, I conceive, be explained 

 in this way: when the saline substances dissolved in sea- 

 water lose their medium of solution, it is obvious they must 

 be precipitated j and even though some of the particles should 

 continue interspersed through the frozen mass, it must be 

 merely in a state of mechanical union. The superincumbent 

 layer of water, however, by slowly percolating through the 

 spongy mass, will gradually wash away those entangled par- 

 ticles. We can thus very readily account for the circumstance 

 of even the portion which is formed from sea-water affording 

 a solution* altogether destitute of saline taste. When, how- 

 ever, this process of filtration is arrested by the deposition of 

 an incumbent layer ofJ'resJi-water ice, which is of a very close 

 texture, these masses will then have a saline taste. 



Professor Lesslie, of Edinburgh, who has thrown much 

 light on this very interesting department of physical science, 

 has lately discovered the singular fact, that frigorific impres- 

 sions are constantly showering down during the day as well 

 as during the night from the higher regions of the atmosphere. 

 From a variety of experiments performed by this philosopher, 

 for the purpose of measuring those pulsations, it appears that 

 the effect varies considerably according to the condition of 

 the higher regions; it is greatest while the sky has the pure 



I have brought large fragments on board ; have melted them, and uni- 

 formly found that the solution was altogether free from the taste of salt- 

 water. 



