330 The Shrinkage of Soils 



Summary. 



1. By determination of the internal pore space in blocks of soils 

 and comparison with the observed value for the linear shrinkage it is 

 found that a linear relationship appears to exist between the two values. 



2. By extrapolating the curve thus obtained an approximation 

 for the limiting value of the shrinkage in the case of pure colloidal 

 clay is arrived at amounting to approximately 23 per cent. 



3. On this assumption it becomes possible to calculate the approxi- 

 mate content of colloidal material in any soil from a knowledge of the 

 linear shrinkage. 



4. Results are adduced, showing the values obtained for the 

 shrinkage in the case of separated fine silt and clay fractions in the case 

 of two soils of known shrinkage and physical composition, and compared 

 with the values calculated from previous assumptions. 



5. The results of the calculation of the content of colloidal clay 

 in the foregoing manner in the case of 16 Leeward Islands soils are 

 appended. 



Acknowledgement is due to Mr E. F. Shepherd for assistance 

 rendered in connection with making many of the measurements referred 

 to in the body of this paper, also to Dr Francis Watts and Mr H. N. 

 Haskell for useful criticisms. 



Government Laboratory for the Leeward Islands, 

 November 18th, 1916. 



{Received Janvxiry lOth, 1917.) 



