210 



This is precisely the effect of frost or intense cold, 

 upon all mineral substances susceptible of its opera- 

 tions, and is that which constitutes one of the criteria, 

 by which we are to determine the extent of its power, 

 in the disintegration and decomposition of rocks. 



It may not be amiss to explain (though it can scarce- 

 ly seem necessary,) the manner in which heat and 

 cold or frost operate to reduce a cubick mass of stone, 

 to that of a spherical form, 



It is, doubtless, well known, that when water is ap- 

 plied to two or more sides of a rock in the form of a 

 cube, or any other angular body capable of imbibing 

 it, the water is gradually absorbed ; as it penetrates 

 the mass from the two sides, it meets at the angles 

 where it is thinest, and its force is then directed diago* 

 nally towards the centre, where the particles of the 

 substance are disposed to receive it, until, perhaps, it 

 becomes saturated ; and that too to a greater distance 

 from the point of the angle towards the centre, than 

 from either of the two sides towards the centre. 



The operations of cold or frost, and heat, are exactly 

 similar. When the cold is sufficiently intense to freeze 

 the mass, to the depth at which the water has penetrated, 

 the particles of the substance are, by the expansion of 

 the water, broken up and displaced. As the cold is 

 abstracted by the application or absorption of heat, 

 which penetrates the mass in the same way or manner, 

 a disintegration of the substances takes place, and ex- 

 tends to the depth to which it was frozen. When this 

 is finished, for the season for instance, the mass no 



