Deerjidd Disruption. 291 



the following manner. The water contained in the ground, 

 (that is, in that part which is within the reach of a freezing 

 temperature) by congealing, expands and demands more space ; 

 a movement must necessarily take place in the direction where 

 there is the least resistance ; this will evidently be upward, 

 because the atmosphere, the only counteracting power in this 

 direction, cannot resist the expansion of the freezing water as 

 much as it is resisted by the earth below the freezing stratum. 

 Consequently, the freezing earth is forced upward, but being 

 of unequal strength in different places, it cracks at the weakest 

 spot ; and the earth, for some distance on the sides of the fissure, 

 is thrown into the position of two planes gently inclined, their 

 relative position reeembling that of a very flat roof, and the 

 more they are lifted by frost, the more they will decline from 

 one another, and the wider will be the fissure. 



But why, in the instance which Mr, Hitchcock has related, 

 did they overlap ? The explanation appears to result from the 

 circumstances of the case, as far as they can be understood 

 without ocular inspection of the ground. 



The elevated spot which cracked in so remarkable a manner, 

 being nearly surrounded by a belt of low wet ground, the con- 

 gelation of the water in this ground by the intense cold, would 

 of course produce a very great expansive effort towards the 

 elevated ground. This, not only on account of its elevation, 

 but from its containing less water, would iiot be able to exert 

 an equal counteracting effort. The surface of the ground, 

 therefore, (without at all disturbing the unfrozen earth below,) 

 was, by the expansive effort of the freezing water, pushed along 

 towards the elevated spot. This spot being possessed of a 

 certain power of resistance derived from its gravityr and from 

 the freezing of the water in it, would not immediately give 

 way ; but the whole surface, it is probable, gradually rose for 

 some time, while the expansion was going on and increasing. 

 A cavity would thus be produced between that superficial 

 layer of frozen ground which was rising, and the unfrozen 

 ground below. This cavity would of course be filled with air 

 derived from the atmosphere, and from, the porousness of the 

 ground below. When the place came to be overflowed, water 



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