H. A. Tempany 325 



The specific gravity of the wax employed for coating the blocks 

 was determined experimentally and found to be '8995 and from the 

 previously ascertained data the volume of the wax coating was calculated 

 and the nett volume of the dried blocks found by deduction. 



Subsequently the apparent density of the blocks was calculated 

 from the data obtained above, the actual density of the soil under 

 examination determined experimentally by means of the specific gravity 

 bottle, and the per cent, pore space in the block calculated by the 

 formula 



P = ^^^ X 100. 



When P is the percentage of pore space in the block D^ is the true 

 density of the soil, and D^ the apparent density of the soil block. 



On these lines the internal pore space was determined on contracted 

 and dried blocks of each of the soils A to E and also on three other 

 soils designated F, G, and H. 



The results of these are given below ; the data are the means of a 

 number of repetitions of each measurement which gave closely agreeing 

 results. 



The data show a regular increase in the pore space corresponding 

 to the observed decrease in the hnear and cubical shrinkage and when 

 the values obtained for the pore space are plotted against the corre- 

 sponding values for the shrinkage the experimental points are found 

 to he very approximately on a straight line (Fig. 4). 



If this curve is extrapolated to cut the vertical ordinate corresponding 

 to the shrinkage per cent, it is found that intersection takes place at 

 a value for the shrinkage of 23-5 per cent. 



The other extremity of the curve cuts the horizontal ordinate at 

 a point corresponding to a pore space of approximately 28 per cent., 

 which value approximates to that of the pore space which is found to 

 exist in uncontracted coarse sand of uniform texture. 



Journ. of Agric. Sci. vni 22 



