232 DISCUSSIONS IN CLIMATOLOGY. 



nearly equally thick. About 60 or 80 feet from the 

 top of an iceberg the strata of ice are a foot or so in 

 thickness, although of a white colour, and thus indi- 

 cating that they contain a quantity of air, and that 

 the particles of ice are not in close apposition, are still 

 very hard, and the specific gravity of the ice is not 

 very much lower than that of layers not more than 

 three inches thick nearer the water-line of the berg. 

 Now it seems to me that this reduction cannot be 

 due to compression alone, and that a portion of the 

 substance of these lower layers must have been 

 removed." * 



If the layers three inches thick near the water-line 

 were once a foot in thickness, as no doubt they were, 

 then this great diminution in thickness cannot have 

 been due to compression ; for, had it been so, the 

 density of those layers would be more than double 

 that of water. But Sir Wyville has found that the 

 specific gravity of the layers three inches thick is not 

 much lower than of those a foot in thickness, which 

 proves, as he has pointed out, that compression cannot 

 account for their thinness; but it does not, as we shall 

 presently see, necessarily prove " that a portion of the 

 substance of these lower layers must have been 

 removed." 



Assuming that the lower layers were all originally 

 of the same thickness as the upper, it has nevertheless 

 been shown in Chapter V. that the gradual diminution 

 in thickness of the layers from the top downwards 

 follows independently altogether of compression or of 

 the removal of any portion of the substance of the 

 layers, either by melting or by any other means. 



Ice radiating from a Centre of Dispersion becomes 

 thinner, because the space over which it is spread 



* "Antarctic Regions," p. 23. 



