THE SHRINKAGE OF SOILS. 



By H. a. TEMPANY, D.Sc. (Lond.), F.I.C, F.C.S., 



Government Chemist and Siqjerintendent of Agricidture 

 for the Leeward Islands. 



The fact that all soils when compacted in a moist condition show 

 a marked decrease in volume on drying is well known. The magnitude 

 of the decrease observed varies in the case of difierent soil types, being 

 greatest as a rule in the case of clay soils and least in those of open sandy 

 texture. The effect is seen in practice in the cracking of the ground 

 surface which occurs during prolonged spells of dry weather, especially 

 in regions in which the prevalent soil type is close grained and heavy. 



The earhest recorded attempts to study and to give numerical 

 expression to this property were made by Schubler, in the course of 

 his work on Soil Physics during the early part of the nineteenth century, 

 who measured the volume contraction exhibited on drying by a number 

 of soils and soil constituents. According to Warington, the actual 

 cubical contraction observed in the case of a number of arable soils 

 ranged from 12 to 15 per cent, of the original volume. 



Until the year 1908 the question does not appear to have been further 

 investigated quantitatively, when at the instance, and under the 

 direction of F. Watts, investigations were undertaken in the West 

 Indies with a view, primarily, to ascertaining whether any connection 

 could be estabUshed between the magnitude of the effect observed 

 in the case of certain soils and the condition of crops growing thereon, 

 notably cacao. 



The results achieved were summarised in a paper by G. G. Auchinleck 

 published in the West Indian Bulletin, vol. xii, pp. 50-69, in which also 

 the methods adopted were described. Briefly these consisted in the 

 addition of water to air-dry soil accompanied by thorough kneading 

 of the sample until the mixture of soil and water had attained its 

 maximum degree of plasticity, the standard assumed being that the 



