536 STUDIES FOR STUDENTS 



The average weight per cubic foot according to these determi- 

 nations was 163.29 pounds. All of the granites tested weighed 

 within five pounds per cubic foot of one another. 



The average weight of twenty-two limestone samples from 

 eleven different quarries was 166.70 pounds per cubic foot. 

 The maximum weight was 176.69 pounds per cubic foot and the 

 minimum 148.50 pounds per cubic foot. The average weight 

 of thirty-two samples of sandstone from sixteen different quar- 

 ries was 136.36 pounds per cubic foot. The maximum weight 

 was 153.63 pounds per cubic foot and the minimum 115.55. 

 pounds per cubic foot. 



POROSITY AND RATIO OF ABSORPTION 



As has been previously pointed out, the porosity gives the 

 volume relation between the pores and the mass of the stone,, 

 while the ratio of absorption gives the weight relation. None 

 of the granites tested had a porosity of more than I per cent., 

 while the porosity of most of the samples was about .45 of 1 per 

 cent. Owing to the interlocking character of the grains, the 

 pores of a granite are much smaller than those of arenaceous 

 limestone or sandstone. The water is therefore taken up and 

 given off very slowly. The ratio of absorption of the granite 

 samples tested was nearly the same as the porosity. 



The limestone samples gave porosities ranging from 13.36' 

 per cent, to .14 of I per cent. The sample having a porosity of 

 13.36 per cent, had a ratio of absorption of about 5.6 per cent. 

 The samples from the Marblehead Lime and Stone Company's 

 quarry, which gave the high crushing and transverse strength 

 tests, had a porosity of about .70 of 1 per cent. 



The porosity of the sandstone samples ranged from 4.81 per 

 cent, to 28.28 per cent. The average porosity of the brown 

 sandstone samples was between 19 and 20 per cent. In the 

 case of the samples of sandstone having a porosity of 28.28 per 

 cent, the ratio of absorption was 15.22 per cent. The Lake 

 Superior brown sandstones gave an average ratio of absorption 

 of less than 10 per cent. 



