176 STUDIES FOR STUDENTS 
The expansive force of freezing water is graphically described 
by Geikie ‘‘as being equal to the weight of a column of ice a 
mile high, or little less than 150 tons to the square foot.”’ One 
centimeter of water at 0° C. occupies 1.0908™ in the form of ice 
at o° C. It is this expansion of about one tenth that does the 
damage when confined water solidifies. . 
Water finds its way into the rocks through openings or hollow 
spaces which are everywhere present. Where the pores are 
large the stone contains water of saturation which is given off 
with comparative readiness, but the nearer the pores or sheet 
cavities approach those of subcapillary size, the greater is the 
tenacity with which the water is retained. One can readily 
understand how the particles composing a rock may be so closely 
fitted together, that the pores will be mainly of subcapillary 
size. Such a rock will contain only the water of imbibition 
which will be given off very slowly, on account of which the 
attendant dangers from freezing will be increasingly great. In 
general it may be said that the danger from freezing will be 
increasingly great as the pores approach in size those of sub- 
capillary dimensions. 
Two rocks, one of which has very minute interstices and the 
other of which has large pores may have a capacity to absorb 
equal amounts of water. The former, however, will be in much 
greater danger from alternate freezing and thawing. Of two 
equally saturated rocks, one with 10 per cent. and the other 
with 3 per cent. of pore space, in which the pores are of equal 
size, the more porous one will be in greater danger of freezing. 
The percentage of the pore space that is filled with water will 
also condition the results of freezing. If two thirds of a rock is 
saturated greater injury will result from its freezing than if only 
one third were saturated. If none of the pores are more than 
nine tenths filled with water, the effect of freezing will be noth- 
ing, because the increased bulk of the frozen water will no more 
than fill the spaces between the grains. 
The amount of water contained in the pores at a given time 
depends, of course, upon the amount of water initially absorbed, 
